feat: implement Simple List API for S3 objects

- Add List method with ListInput and ListResponse structs following simples3 patterns
- Implement pagination, prefix filtering, and delimiter grouping
- Add comprehensive test suite for List functionality
- Update tests to use environment variables instead of hardcoded values
- Fix deprecated io/ioutil usage throughout codebase
- Add comprehensive README with API documentation and examples
- Add Nix development environment with flake.nix
- Add Justfile for modern command runner
- Add Docker Compose setup for local MinIO testing
- Update GitHub Actions to use Nix and Justfile for CI consistency
- Fix test naming and setup flow issues

New API:
s3.List(ListInput{
    Bucket: "my-bucket",
    Prefix: "documents/",
    MaxKeys: 100,
})

All tests pass with new simplified API design.

.envrc

@@ -0,0 +1,4 @@
+# Load the Nix development environment
+use flake
+
+echo "✅ Environment loaded - Use 'just --list' to see available commands"

.github/workflows/go-test.yml

@@ -10,31 +10,19 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+      - name: Checkout code
+        uses: actions/checkout@v4
 
-    - name: Set up Go
+      - name: Install Nix
-      uses: actions/setup-go@v2
+        uses: cachix/install-nix-action@v27
-      with:
+        with:
-        go-version: 1.15
+          nix_path: nixpkgs=channel:nixos-unstable
-    - name: Setup minio
+
-      run: |
+      - name: Run Tests via Justfile
-          docker run -d -p 9000:9000 --name minio \
+        env:
-                     -e "MINIO_ACCESS_KEY=minioadmin" \
+          AWS_S3_BUCKET: testbucket
-                     -e "MINIO_SECRET_KEY=minioadmin" \
+          AWS_ACCESS_KEY_ID: minioadmin
-                     -v /tmp/data:/data \
+          AWS_SECRET_ACCESS_KEY: minioadmin
-                     -v /tmp/config:/root/.minio \
+          AWS_S3_ENDPOINT: http://127.0.0.1:9000
-                     minio/minio server /data
+          AWS_EC2_METADATA_DISABLED: "true"
-                     
+        run: nix develop --command just test-local
-          export AWS_ACCESS_KEY_ID=minioadmin
-          export AWS_SECRET_ACCESS_KEY=minioadmin
-          export AWS_EC2_METADATA_DISABLED=true
-          
-          aws --endpoint-url http://127.0.0.1:9000/ s3 mb s3://testbucket
-           
-    - name: Run Go Test
-      run: go test -v ./...
-      env:
-        AWS_S3_BUCKET: testbucket 
-        AWS_S3_ACCESS_KEY: minioadmin
-        AWS_S3_SECRET_KEY: minioadmin
-        AWS_S3_ENDPOINT: http://127.0.0.1:9000

.gitignore

@@ -24,3 +24,6 @@ tsconfig.json
 jsconfig.json
 
 .env
+
+# direnv
+.direnv

Justfile

@@ -0,0 +1,92 @@
+# SimpleS3 Development Commands
+
+# Variables
+MINIO_CONTAINER_NAME := "simples3-minio"
+MINIO_DATA_DIR := ".minio-data"
+AWS_S3_BUCKET := "testbucket"
+
+# Default command - lists all available recipes
+default:
+    @just --list
+
+# --- Development Commands ---
+test:
+    @echo "🧪 Running all tests..."
+    @go test -v ./...
+
+test-local: setup
+    @echo "🧪 Running tests with local MinIO..."
+    @sleep 2
+    @go test -v ./...
+
+
+# --- Go Module Management ---
+tidy:
+    @echo "📦 Tidying Go modules..."
+    @go mod tidy
+
+fmt:
+    @echo "🎨 Formatting Go code..."
+    @go fmt ./...
+
+vet:
+    @echo "🔍 Running go vet..."
+    @go vet ./...
+
+# --- MinIO Management ---
+minio-up:
+    @echo "🚀 Starting MinIO container..."
+    @docker compose up -d
+    @echo "✅ MinIO started:"
+    @echo "   API: http://localhost:9000"
+    @echo "   Console: http://localhost:9001"
+    @echo "   Access Key: minioadmin"
+    @echo "   Secret Key: minioadmin"
+
+minio-down:
+    @echo "🛑 Stopping MinIO container..."
+    @docker compose down
+
+minio-logs:
+    @echo "📋 Showing MinIO logs..."
+    @docker compose logs -f
+
+minio-clean:
+    @echo "🧹 Cleaning MinIO data..."
+    @docker compose down --volumes
+
+minio-reset: minio-clean minio-up
+
+# --- Development Environment Setup ---
+setup: minio-up
+    @echo "⚙️ Setting up development environment..."
+    @sleep 3
+    @aws --endpoint-url http://127.0.0.1:9000/ s3 mb s3://{{AWS_S3_BUCKET}} || true
+    @echo "✅ Development environment ready!"
+
+dev-env: setup
+    @echo "🎯 Development environment active!"
+    @echo "   MinIO: http://localhost:9000"
+    @echo "   Console: http://localhost:9001"
+    @echo "   Bucket: {{AWS_S3_BUCKET}}"
+
+# --- Cleanup Commands ---
+clean:
+    @echo "🧹 Cleaning up development environment..."
+    @docker compose down --volumes
+
+# --- Helper Commands ---
+status:
+    @echo "📊 Status Check:"
+    @echo "   MinIO Container: $(docker ps -q -f name={{MINIO_CONTAINER_NAME}} | wc -l | tr -d ' ') running"
+    @if [ "$(docker ps -q -f name={{MINIO_CONTAINER_NAME}})" ]; then \
+        echo "   MinIO URL: http://localhost:9000"; \
+        echo "   Console URL: http://localhost:9001"; \
+    fi
+    @echo "   Go version: $(go version | awk '{print $3}')"
+
+# --- Documentation ---
+docs:
+    @echo "📖 Opening documentation..."
+    @echo "   Plan: PLAN.md"
+    @echo "   README: README.md"

README.md

@@ -1,82 +1,334 @@
 # simples3 : Simple no frills AWS S3 Library using REST with V4 Signing
 
-## Overview [![GoDoc](https://godoc.org/github.com/rhnvrm/simples3?status.svg)](https://godoc.org/github.com/rhnvrm/simples3) [![Go Report Card](https://goreportcard.com/badge/github.com/rhnvrm/simples3)](https://goreportcard.com/report/github.com/rhnvrm/simples3) [![GoCover](https://gocover.io/_badge/github.com/rhnvrm/simples3)](https://gocover.io/_badge/github.com/rhnvrm/simples3) [![Zerodha Tech](https://zerodha.tech/static/images/github-badge.svg)](https://zerodha.tech) 
+## Overview [![GoDoc](https://godoc.org/github.com/rhnvrm/simples3?status.svg)](https://godoc.org/github.com/rhnvrm/simples3) [![Go Report Card](https://goreportcard.com/badge/github.com/rhnvrm/simples3)](https://goreportcard.com/report/github.com/rhnvrm/simples3) [![GoCover](https://gocover.io/_badge/github.com/rhnvrm/simples3)](https://gocover.io/_badge/github.com/rhnvrm/simples3) [![Zerodha Tech](https://zerodha.tech/static/images/github-badge.svg)](https://zerodha.tech)
 
-SimpleS3 is a Go library for manipulating objects 
+SimpleS3 is a Go library for manipulating objects
-in S3 buckets using REST API calls or Presigned URLs signed 
+in S3 buckets using REST API calls or Presigned URLs signed
 using AWS Signature Version 4.
 
+**Features:**
+- 🚀 **Simple, intuitive API** following Go idioms
+- 🪣 **Complete S3 operations** - Upload, Download, Delete, List, Details
+- 🔐 **AWS Signature Version 4** signing
+- 🌐 **Custom endpoint support** (MinIO, DigitalOcean Spaces, etc.)
+- 📋 **Simple List API** with pagination, prefix filtering, and delimiter grouping
+- 🔗 **Presigned URL generation** for secure browser uploads/downloads
+- 🪪 **IAM credential support** for EC2 instances
+- ✅ **Comprehensive test coverage**
+- 🎯 **Zero dependencies** - uses only Go standard library
+
 ## Install
 
 ```sh
 go get github.com/rhnvrm/simples3
 ```
 
-## Example
+## Quick Start
 
 ```go
-testTxt, _ := os.Open("testdata/test.txt")
+package main
-defer testTxt.Close()
 
-// Create an instance of the package
+import (
-// You can either create by manually supplying credentials
+    "log"
-// (preferably using Environment vars)
+    "os"
-s3 := simples3.New(Region, AWSAccessKey, AWSSecretKey)
+    "github.com/rhnvrm/simples3"
-// or you can use this on an EC2 instance to 
+)
-// obtain credentials from IAM attached to the instance.
-s3, _ := simples3.NewUsingIAM(Region)
 
-// You can also set a custom endpoint to a compatible s3 instance. 
+func main() {
-s3.SetEndpoint(CustomEndpoint)
+    // Initialize S3 client
+    s3 := simples3.New("us-east-1", "your-access-key", "your-secret-key")
 
-// Note: Consider adding a testTxt.Seek(0, 0)
+    // Use MinIO or other S3-compatible services
-// in case you have read 
+    s3.SetEndpoint("https://s3.amazonaws.com")
-// the body, as the pointer is shared by the library.
 
-// File Upload is as simple as providing the following
+    // Upload a file
-// details.
+    file, _ := os.Open("my-file.txt")
+    defer file.Close()
+
+    resp, err := s3.FileUpload(simples3.UploadInput{
+        Bucket:      "my-bucket",
+        ObjectKey:   "my-file.txt",
+        ContentType: "text/plain",
+        FileName:    "my-file.txt",
+        Body:        file,
+    })
+    if err != nil {
+        log.Fatal(err)
+    }
+
+    log.Printf("File uploaded successfully: %+v", resp)
+}
+```
+
+## API Reference
+
+### File Operations
+
+#### Upload Files
+```go
+// POST upload (recommended for browsers)
 resp, err := s3.FileUpload(simples3.UploadInput{
-    Bucket:      AWSBucket,
+    Bucket:      "my-bucket",
-    ObjectKey:   "test.txt",
+    ObjectKey:   "path/to/file.txt",
     ContentType: "text/plain",
-    FileName:    "test.txt",
+    FileName:    "file.txt",
-    Body:        testTxt,
+    Body:        file,
 })
 
-// Similarly, Files can be deleted.
+// PUT upload (simpler for programmatic use)
+resp, err := s3.FilePut(simples3.UploadInput{
+    Bucket:      "my-bucket",
+    ObjectKey:   "path/to/file.txt",
+    ContentType: "text/plain",
+    Body:        file,
+})
+```
+
+#### Download Files
+```go
+// Download file
+file, err := s3.FileDownload(simples3.DownloadInput{
+    Bucket:    "my-bucket",
+    ObjectKey: "path/to/file.txt",
+})
+if err != nil {
+    log.Fatal(err)
+}
+defer file.Close()
+
+// Read the content
+data, err := io.ReadAll(file)
+```
+
+#### Delete Files
+```go
 err := s3.FileDelete(simples3.DeleteInput{
-    Bucket:    os.Getenv("AWS_S3_BUCKET"),
+    Bucket:    "my-bucket",
-    ObjectKey: "test.txt",
+    ObjectKey: "path/to/file.txt",
 })
+```
 
-// You can also download the file.
+#### Get File Details
-file, _ := s3.FileDownload(simples3.DownloadInput{
+```go
-    Bucket:    AWSBucket,
+details, err := s3.FileDetails(simples3.DetailsInput{
-    ObjectKey: "test.txt",
+    Bucket:    "my-bucket",
+    ObjectKey: "path/to/file.txt",
 })
+if err != nil {
+    log.Fatal(err)
+}
 
-data, _ := ioutil.ReadAll(file)
+log.Printf("File size: %s bytes", details.ContentLength)
-file.Close()
+log.Printf("Last modified: %s", details.LastModified)
+log.Printf("Content type: %s", details.ContentType)
+```
 
-// You can also use this library to generate
+### List Objects
-// Presigned URLs that can for eg. be used to
-// GET/PUT files on S3 through the browser.
-var time, _ = time.Parse(time.RFC1123, "Fri, 24 May 2013 00:00:00 GMT")
 
-url := s.GeneratePresignedURL(PresignedInput{
+SimpleS3 provides a clean, easy-to-use List API that follows the same pattern as other library methods:
-    Bucket:        AWSBucket,
+
-    ObjectKey:     "test.txt",
+#### Simple Listing
+```go
+// List all objects in a bucket
+result, err := s3.List(simples3.ListInput{
+    Bucket: "my-bucket",
+})
+if err != nil {
+    log.Fatal(err)
+}
+
+fmt.Printf("Found %d objects:\n", len(result.Objects))
+for _, obj := range result.Objects {
+    fmt.Printf("- %s (%d bytes)\n", obj.Key, obj.Size)
+}
+```
+
+#### Advanced Listing with Options
+```go
+// List with prefix filtering and pagination
+result, err := s3.List(simples3.ListInput{
+    Bucket:    "my-bucket",
+    Prefix:    "documents/",
+    Delimiter: "/",
+    MaxKeys:   100,
+})
+if err != nil {
+    log.Fatal(err)
+}
+
+// Process objects
+for _, obj := range result.Objects {
+    fmt.Printf("📄 %s (%d bytes)\n", obj.Key, obj.Size)
+}
+
+// Process "directories" (common prefixes)
+for _, prefix := range result.CommonPrefixes {
+    fmt.Printf("📁 %s/\n", prefix)
+}
+```
+
+#### Handle Pagination
+```go
+// Handle large result sets with pagination
+func listAllObjects(s3 *simples3.S3, bucket string) ([]simples3.Object, error) {
+    var allObjects []simples3.Object
+    var continuationToken string
+
+    for {
+        // List objects with continuation token
+        result, err := s3.List(simples3.ListInput{
+            Bucket:            bucket,
+            ContinuationToken: continuationToken,
+            MaxKeys:          1000, // Maximum page size
+        })
+        if err != nil {
+            return nil, err
+        }
+
+        // Add current page objects to our collection
+        allObjects = append(allObjects, result.Objects...)
+
+        // Check if there are more pages
+        if !result.IsTruncated {
+            break
+        }
+
+        // Set token for next page
+        continuationToken = result.NextContinuationToken
+    }
+
+    return allObjects, nil
+}
+
+// Usage example
+func main() {
+    s3 := simples3.New("us-east-1", "your-access-key", "your-secret-key")
+
+    allObjects, err := listAllObjects(s3, "my-bucket")
+    if err != nil {
+        log.Fatal(err)
+    }
+
+    fmt.Printf("Total objects: %d\\n", len(allObjects))
+    for _, obj := range allObjects {
+        fmt.Printf("- %s (%d bytes)\\n", obj.Key, obj.Size)
+    }
+}
+```
+
+### Presigned URLs
+
+Generate secure URLs for browser-based uploads/downloads:
+
+```go
+// Generate presigned URL for download
+url := s3.GeneratePresignedURL(simples3.PresignedInput{
+    Bucket:        "my-bucket",
+    ObjectKey:     "private-file.pdf",
     Method:        "GET",
-    Timestamp:     time,
+    ExpirySeconds: 3600, // 1 hour
-    ExpirySeconds: 86400,
 })
+
+// Users can now download directly: <a href="{{url}}">Download</a>
+```
+
+### Custom Endpoints
+
+Use with MinIO, DigitalOcean Spaces, or other S3-compatible services:
+
+```go
+// MinIO
+s3 := simples3.New("us-east-1", "minioadmin", "minioadmin")
+s3.SetEndpoint("http://localhost:9000")
+
+// DigitalOcean Spaces
+s3 := simples3.New("nyc3", "your-access-key", "your-secret-key")
+s3.SetEndpoint("https://nyc3.digitaloceanspaces.com")
+```
+
+### IAM Credentials
+
+On EC2 instances, use IAM roles automatically:
+
+```go
+s3, err := simples3.NewUsingIAM("us-east-1")
+if err != nil {
+    log.Fatal(err)
+}
+// Automatically uses instance IAM role
+```
+
+## Development
+
+### Setup Development Environment
+
+```sh
+# Clone the repository
+git clone https://github.com/rhnvrm/simples3.git
+cd simples3
+
+# Using Nix (recommended)
+nix develop
+
+# Or using direnv
+direnv allow
+
+# Start local MinIO for testing
+just setup
+
+# Run tests
+just test-local
+```
+
+### Testing
+
+The library includes comprehensive tests that run against a local MinIO instance:
+
+```sh
+# Run all tests (without MinIO)
+just test
+
+# Run tests with local MinIO
+just test-local
+
+# Run specific test
+go test -v -run TestList
+```
+
+### Available Commands
+
+```sh
+just              # List all commands
+just test         # Run tests without MinIO
+just test-local   # Run tests with MinIO (includes setup)
+just setup        # Setup development environment
+just minio-up      # Start MinIO container
+just minio-down    # Stop MinIO container
+just clean         # Clean up everything
+just status        # Check development environment status
+```
+
+## Environment Variables
+
+For development and testing:
+
+```sh
+export AWS_S3_REGION="us-east-1"
+export AWS_S3_ACCESS_KEY="minioadmin"
+export AWS_S3_SECRET_KEY="minioadmin"
+export AWS_S3_ENDPOINT="http://localhost:9000"
+export AWS_S3_BUCKET="testbucket"
 ```
 
 ## Contributing
 
-You are more than welcome to contribute to this project. Fork and make 
+We welcome contributions! Please:
-a Pull Request, or create an Issue if you see any problem or want to
+
-propose a feature.
+1. Fork the repository
+2. Create a feature branch
+3. Add tests for new functionality
+4. Ensure all tests pass: `just test-local`
+5. Submit a pull request
 
 ## Author
 

docker-compose.yml

@@ -0,0 +1,21 @@
+services:
+  minio:
+    image: minio/minio:latest
+    container_name: simples3-minio
+    ports:
+      - "9000:9000"   # API
+      - "9001:9001"   # Console
+    environment:
+      - MINIO_ROOT_USER=minioadmin
+      - MINIO_ROOT_PASSWORD=minioadmin
+    volumes:
+      - minio_data:/data
+    command: server /data --console-address ":9001"
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:9000/minio/health/live"]
+      interval: 30s
+      timeout: 20s
+      retries: 3
+
+volumes:
+  minio_data:

flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1757745802,
+        "narHash": "sha256-hLEO2TPj55KcUFUU1vgtHE9UEIOjRcH/4QbmfHNF820=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "c23193b943c6c689d70ee98ce3128239ed9e32d1",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,62 @@
+{
+  description = "Go project for simples3 with ListObjectsV2 support";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+  };
+
+  outputs = { self, nixpkgs }:
+    let
+      supportedSystems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
+      forEachSystem = f: nixpkgs.lib.genAttrs supportedSystems (system: f {
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+      });
+    in
+    {
+      devShells = forEachSystem ({ pkgs }: {
+        default = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            # Go development
+            go
+            gopls
+            go-outline
+            delve
+
+            # Build tools and utilities
+            just
+            docker
+            awscli2
+
+            # Additional utilities
+            curl
+            jq
+          ];
+
+          # Environment variables for the shell
+          shellHook = ''
+            echo "🚀 SimpleS3 Development Environment Loaded"
+            echo "Go version: $(go version)"
+            echo "Available commands: just --list"
+            export GOPATH=$(go env GOPATH)
+            export PATH=$PATH:$GOPATH/bin
+
+            # Local S3 (MinIO) configuration for testing
+            export AWS_S3_BUCKET=testbucket
+            export AWS_S3_ENDPOINT=http://localhost:9000
+            export AWS_S3_REGION=us-east-1
+            export AWS_EC2_METADATA_DISABLED=true
+
+            # AWS CLI credentials for MinIO
+            export AWS_ACCESS_KEY_ID=minioadmin
+            export AWS_SECRET_ACCESS_KEY=minioadmin
+
+            # Simples3 library credentials
+            export AWS_S3_ACCESS_KEY=minioadmin
+            export AWS_S3_SECRET_KEY=minioadmin
+          '';
+        };
+      });
+    };
+}

go.mod

@@ -1,3 +1,3 @@
 module github.com/rhnvrm/simples3
 
-go 1.13
+go 1.25.0

policy.go

@@ -152,7 +152,7 @@ func buildUploadSign(nowTime time.Time, credential string, uploadConfig UploadCo
 	})
 }
 
-func (s3 S3) buildCredential(nowTime time.Time) []byte {
+func (s3 *S3) buildCredential(nowTime time.Time) []byte {
 	var b bytes.Buffer
 	b.WriteString(s3.AccessKey)
 	b.WriteRune('/')
@@ -166,7 +166,7 @@ func (s3 S3) buildCredential(nowTime time.Time) []byte {
 	return b.Bytes()
 }
 
-func (s3 S3) buildCredentialWithoutKey(nowTime time.Time) []byte {
+func (s3 *S3) buildCredentialWithoutKey(nowTime time.Time) []byte {
 	var b bytes.Buffer
 	b.WriteString(nowTime.Format(shortTimeFormat))
 	b.WriteRune('/')

simples3.go

@@ -12,9 +12,9 @@ import (
 	"encoding/xml"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"mime/multipart"
 	"net/http"
+	"net/url"
 	"regexp"
 	"strings"
 	"sync"
@@ -126,6 +126,80 @@ type DeleteInput struct {
 	ObjectKey string
 }
 
+// ListInput is passed to List as a parameter.
+type ListInput struct {
+	// Required: The name of the bucket to list objects from
+	Bucket string
+
+	// Optional: A delimiter to group objects by (commonly "/")
+	Delimiter string
+
+	// Optional: Only list objects starting with this prefix
+	Prefix string
+
+	// Optional: Maximum number of objects to return
+	MaxKeys int64
+
+	// Optional: Token for pagination from a previous request
+	ContinuationToken string
+
+	// Optional: Object key to start listing after
+	StartAfter string
+}
+
+// ListResponse is returned by List.
+type ListResponse struct {
+	// Name of the bucket
+	Name string
+
+	// Whether the results were truncated (more results available)
+	IsTruncated bool
+
+	// Token to get the next page of results (if truncated)
+	NextContinuationToken string
+
+	// List of objects in the bucket
+	Objects []Object
+
+	// Common prefixes when using delimiter (like directories)
+	CommonPrefixes []string
+
+	// Total number of keys returned
+	KeyCount int64
+}
+
+// Object represents an S3 object in a bucket.
+type Object struct {
+	// Name of the object
+	Key string
+
+	// Size in bytes
+	Size int64
+
+	// When the object was last modified
+	LastModified string
+
+	// Entity tag of the object
+	ETag string
+
+	// Storage class (e.g., "STANDARD")
+	StorageClass string
+}
+
+// S3Error represents an S3 API error response
+type S3Error struct {
+	XMLName   xml.Name `xml:"Error"`
+	Code      string   `xml:"Code"`
+	Message   string   `xml:"Message"`
+	RequestID string   `xml:"RequestId"`
+	HostID    string   `xml:"HostId"`
+}
+
+// Error returns a string representation of the S3Error
+func (e S3Error) Error() string {
+	return fmt.Sprintf("S3 Error: %s - %s", e.Code, e.Message)
+}
+
 // IAMResponse is used by NewUsingIAM to auto
 // detect the credentials.
 type IAMResponse struct {
@@ -179,14 +253,14 @@ func fetchIMDSToken(cl *http.Client, baseURL string) (string, bool, error) {
 
 	defer func() {
 		resp.Body.Close()
-		io.Copy(ioutil.Discard, resp.Body)
+		io.Copy(io.Discard, resp.Body)
 	}()
 
 	if resp.StatusCode != http.StatusOK {
 		return "", false, fmt.Errorf("failed to request IMDSv2 token: %s", resp.Status)
 	}
 
-	token, err := ioutil.ReadAll(resp.Body)
+	token, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return "", false, err
 	}
@@ -224,12 +298,12 @@ func fetchIAMData(cl *http.Client, baseURL string) (IAMResponse, error) {
 		return IAMResponse{}, fmt.Errorf("error fetching IAM data: %s", resp.Status)
 	}
 
-	role, err := ioutil.ReadAll(resp.Body)
+	role, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return IAMResponse{}, err
 	}
 
-	_, _ = io.Copy(ioutil.Discard, resp.Body)
+	_, _ = io.Copy(io.Discard, resp.Body)
 	_ = resp.Body.Close()
 
 	req, err = http.NewRequest(http.MethodGet, url+string(role), nil)
@@ -247,7 +321,7 @@ func fetchIAMData(cl *http.Client, baseURL string) (IAMResponse, error) {
 
 	defer func() {
 		// Drain and close the body to let the Transport reuse the connection
-		io.Copy(ioutil.Discard, resp.Body)
+		io.Copy(io.Discard, resp.Body)
 		resp.Body.Close()
 	}()
 
@@ -256,7 +330,7 @@ func fetchIAMData(cl *http.Client, baseURL string) (IAMResponse, error) {
 	}
 
 	var jResp IAMResponse
-	jsonString, err := ioutil.ReadAll(resp.Body)
+	jsonString, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return IAMResponse{}, fmt.Errorf("error reading role data: %w", err)
 	}
@@ -536,10 +610,10 @@ func (s3 *S3) FilePut(u UploadInput) (PutResponse, error) {
 
 	defer func() {
 		res.Body.Close()
-		io.Copy(ioutil.Discard, res.Body)
+		io.Copy(io.Discard, res.Body)
 	}()
 
-	data, err := ioutil.ReadAll(res.Body)
+	data, err := io.ReadAll(res.Body)
 	if err != nil {
 		return PutResponse{}, err
 	}
@@ -635,10 +709,10 @@ func (s3 *S3) FileUpload(u UploadInput) (UploadResponse, error) {
 
 	defer func() {
 		res.Body.Close()
-		io.Copy(ioutil.Discard, res.Body)
+		io.Copy(io.Discard, res.Body)
 	}()
 
-	data, err := ioutil.ReadAll(res.Body)
+	data, err := io.ReadAll(res.Body)
 	if err != nil {
 		return UploadResponse{}, err
 	}
@@ -680,7 +754,7 @@ func (s3 *S3) FileDelete(u DeleteInput) error {
 
 	defer func() {
 		res.Body.Close()
-		io.Copy(ioutil.Discard, res.Body)
+		io.Copy(io.Discard, res.Body)
 	}()
 
 	// Check the response
@@ -714,7 +788,7 @@ func (s3 *S3) FileDetails(u DetailsInput) (DetailsResponse, error) {
 
 	defer func() {
 		res.Body.Close()
-		io.Copy(ioutil.Discard, res.Body)
+		io.Copy(io.Discard, res.Body)
 	}()
 
 	if res.StatusCode != http.StatusOK {
@@ -764,6 +838,141 @@ func (s3 *S3) FileDetails(u DetailsInput) (DetailsResponse, error) {
 	return out, nil
 }
 
+// List implements a simple S3 object listing API
+func (s3 *S3) List(input ListInput) (ListResponse, error) {
+	// Input validation
+	if input.Bucket == "" {
+		return ListResponse{}, fmt.Errorf("bucket name cannot be empty")
+	}
+	if input.MaxKeys < 0 {
+		return ListResponse{}, fmt.Errorf("MaxKeys cannot be negative")
+	}
+	if input.MaxKeys > 1000 {
+		return ListResponse{}, fmt.Errorf("MaxKeys cannot exceed 1000")
+	}
+
+	// Build query parameters - ListObjectsV2 uses query params, not path
+	query := url.Values{}
+	query.Set("list-type", "2") // Required parameter
+
+	// Add optional parameters if they exist
+	if input.ContinuationToken != "" {
+		query.Set("continuation-token", input.ContinuationToken)
+	}
+	if input.Delimiter != "" {
+		query.Set("delimiter", input.Delimiter)
+	}
+	if input.MaxKeys > 0 {
+		query.Set("max-keys", fmt.Sprintf("%d", input.MaxKeys))
+	}
+	if input.Prefix != "" {
+		query.Set("prefix", input.Prefix)
+	}
+	if input.StartAfter != "" {
+		query.Set("start-after", input.StartAfter)
+	}
+
+	// Build base URL
+	baseURL := s3.getURL(input.Bucket)
+
+	// Parse URL and add query parameters
+	parsedURL, err := url.Parse(baseURL)
+	if err != nil {
+		return ListResponse{}, err
+	}
+	parsedURL.RawQuery = query.Encode()
+
+	// Create HTTP request
+	req, err := http.NewRequest(http.MethodGet, parsedURL.String(), nil)
+	if err != nil {
+		return ListResponse{}, err
+	}
+
+	// Apply AWS V4 signing
+	if err := s3.renewIAMToken(); err != nil {
+		return ListResponse{}, err
+	}
+	if err := s3.signRequest(req); err != nil {
+		return ListResponse{}, err
+	}
+
+	// Execute request
+	client := s3.getClient()
+	res, err := client.Do(req)
+	if err != nil {
+		return ListResponse{}, err
+	}
+
+	// Close response body when done
+	defer res.Body.Close()
+
+	// Read response body once
+	body, err := io.ReadAll(res.Body)
+	if err != nil {
+		return ListResponse{}, err
+	}
+
+	// Handle response status codes
+	if res.StatusCode != http.StatusOK {
+		var s3Err S3Error
+		if xmlErr := xml.Unmarshal(body, &s3Err); xmlErr == nil {
+			return ListResponse{}, fmt.Errorf("S3 Error: %s - %s", s3Err.Code, s3Err.Message)
+		}
+		return ListResponse{}, fmt.Errorf("status code: %s: %s", res.Status, string(body))
+	}
+
+	// Parse XML response using internal struct
+	var xmlResult struct {
+		XMLName              xml.Name `xml:"ListBucketResult"`
+		Name                 string   `xml:"Name"`
+		IsTruncated          bool     `xml:"IsTruncated"`
+		NextContinuationToken string   `xml:"NextContinuationToken"`
+		KeyCount             int64    `xml:"KeyCount"`
+		Contents             []struct {
+			Key          string `xml:"Key"`
+			LastModified string `xml:"LastModified"`
+			ETag         string `xml:"ETag"`
+			Size         int64  `xml:"Size"`
+			StorageClass string `xml:"StorageClass"`
+		} `xml:"Contents"`
+		CommonPrefixes []struct {
+			Prefix string `xml:"Prefix"`
+		} `xml:"CommonPrefixes"`
+	}
+
+	if err := xml.Unmarshal(body, &xmlResult); err != nil {
+		return ListResponse{}, err
+	}
+
+	// Convert to simple response format
+	response := ListResponse{
+		Name:                  xmlResult.Name,
+		IsTruncated:           xmlResult.IsTruncated,
+		NextContinuationToken: xmlResult.NextContinuationToken,
+		KeyCount:             xmlResult.KeyCount,
+	}
+
+	// Convert objects
+	for _, obj := range xmlResult.Contents {
+		response.Objects = append(response.Objects, Object{
+			Key:          obj.Key,
+			Size:         obj.Size,
+			LastModified: obj.LastModified,
+			ETag:         obj.ETag,
+			StorageClass: obj.StorageClass,
+		})
+	}
+
+	// Convert common prefixes
+	for _, prefix := range xmlResult.CommonPrefixes {
+		response.CommonPrefixes = append(response.CommonPrefixes, prefix.Prefix)
+	}
+
+	return response, nil
+}
+
+
+
 func getFirstString(s []string) string {
 	if len(s) > 0 {
 		return s[0]

simples3_test.go

@@ -3,12 +3,13 @@ package simples3
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"io"
-	"io/ioutil"
 	"net"
 	"net/http"
 	"net/http/httptest"
 	"os"
+	"strings"
 	"testing"
 	"time"
 )
@@ -23,18 +24,18 @@ type tConfig struct {
 func TestS3_FileUploadPostAndPut(t *testing.T) {
 	testTxt, err := os.Open("testdata/test.txt")
 	if err != nil {
-		return
+		t.Fatalf("Failed to open test.txt: %v", err)
 	}
 	defer testTxt.Close()
 	// Note: cannot re-use the same file descriptor due to seeking!
 	testTxtSpecialChars, err := os.Open("testdata/test.txt")
 	if err != nil {
-		return
+		t.Fatalf("Failed to open test.txt for special chars: %v", err)
 	}
 	defer testTxtSpecialChars.Close()
 	testPng, err := os.Open("testdata/avatar.png")
 	if err != nil {
-		return
+		t.Fatalf("Failed to open avatar.png: %v", err)
 	}
 	defer testPng.Close()
 
@@ -204,7 +205,7 @@ func TestS3_FileDownload(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer testTxt.Close()
-	testTxtData, err := ioutil.ReadAll(testTxt)
+	testTxtData, err := io.ReadAll(testTxt)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -214,7 +215,7 @@ func TestS3_FileDownload(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer testPng.Close()
-	testPngData, err := ioutil.ReadAll(testPng)
+	testPngData, err := io.ReadAll(testPng)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -292,7 +293,7 @@ func TestS3_FileDownload(t *testing.T) {
 				t.Fatalf("S3.FileDownload() error = %v, wantErr %v", err, tt.wantErr)
 			}
 
-			got, err := ioutil.ReadAll(resp)
+			got, err := io.ReadAll(resp)
 			if err != nil {
 				t.Fatalf("error = %v", err)
 			}
@@ -568,3 +569,209 @@ func TestGetURL(t *testing.T) {
 		})
 	}
 }
+
+func TestList(t *testing.T) {
+	// Setup test environment
+	s3 := New(
+		os.Getenv("AWS_S3_REGION"),
+		os.Getenv("AWS_S3_ACCESS_KEY"),
+		os.Getenv("AWS_S3_SECRET_KEY"),
+	)
+	s3.SetEndpoint(os.Getenv("AWS_S3_ENDPOINT"))
+
+	// Test cases
+	tests := []struct {
+		name     string
+		setup    func() // Setup function to prepare test data
+		input    ListInput
+		validate func(ListResponse, error)
+		cleanup  func() // Cleanup function
+	}{
+		{
+			name: "Empty Bucket",
+			input: ListInput{
+				Bucket: os.Getenv("AWS_S3_BUCKET"),
+			},
+			validate: func(result ListResponse, err error) {
+				if err != nil {
+					t.Fatalf("Expected no error, got %v", err)
+				}
+				if len(result.Objects) != 0 {
+					t.Errorf("Expected empty bucket, got %d objects", len(result.Objects))
+				}
+			},
+		},
+		{
+			name: "Basic Listing",
+			setup: func() {
+				// Upload test files
+				uploadTestFiles(t, s3, os.Getenv("AWS_S3_BUCKET"), []string{"file1.txt", "file2.txt", "file3.txt"})
+			},
+			input: ListInput{
+				Bucket: os.Getenv("AWS_S3_BUCKET"),
+			},
+			validate: func(result ListResponse, err error) {
+				if err != nil {
+					t.Fatalf("Expected no error, got %v", err)
+				}
+				if len(result.Objects) != 3 {
+					t.Errorf("Expected 3 objects, got %d", len(result.Objects))
+				}
+			},
+			cleanup: func() {
+				cleanupTestFiles(t, s3, os.Getenv("AWS_S3_BUCKET"), []string{"file1.txt", "file2.txt", "file3.txt"})
+			},
+		},
+		{
+			name: "Pagination Test",
+			setup: func() {
+				// Upload many files for pagination testing
+				var filenames []string
+				for i := 1; i <= 25; i++ {
+					filenames = append(filenames, fmt.Sprintf("file%03d.txt", i))
+				}
+				uploadTestFiles(t, s3, os.Getenv("AWS_S3_BUCKET"), filenames)
+			},
+			input: ListInput{
+				Bucket:  os.Getenv("AWS_S3_BUCKET"),
+				MaxKeys: 10,
+			},
+			validate: func(result ListResponse, err error) {
+				if err != nil {
+					t.Fatalf("Expected no error, got %v", err)
+				}
+				if len(result.Objects) != 10 {
+					t.Errorf("Expected 10 objects, got %d", len(result.Objects))
+				}
+				if !result.IsTruncated {
+					t.Errorf("Expected IsTruncated=true for pagination")
+				}
+				if result.NextContinuationToken == "" {
+					t.Errorf("Expected NextContinuationToken for pagination: %v", result.NextContinuationToken)
+				}
+			},
+			cleanup: func() {
+				var filenames []string
+				for i := 1; i <= 25; i++ {
+					filenames = append(filenames, fmt.Sprintf("file%03d.txt", i))
+				}
+				cleanupTestFiles(t, s3, os.Getenv("AWS_S3_BUCKET"), filenames)
+			},
+		},
+		{
+			name: "Prefix Filtering",
+			setup: func() {
+				uploadTestFiles(t, s3, os.Getenv("AWS_S3_BUCKET"), []string{
+					"documents/file1.txt",
+					"documents/file2.txt",
+					"images/image1.jpg",
+					"images/image2.jpg",
+				})
+			},
+			input: ListInput{
+				Bucket: os.Getenv("AWS_S3_BUCKET"),
+				Prefix: "documents/",
+			},
+			validate: func(result ListResponse, err error) {
+				if err != nil {
+					t.Fatalf("Expected no error, got %v", err)
+				}
+				if len(result.Objects) != 2 {
+					t.Errorf("Expected 2 objects with documents/ prefix, got %d", len(result.Objects))
+				}
+				for _, obj := range result.Objects {
+					if !strings.HasPrefix(obj.Key, "documents/") {
+						t.Errorf("Object %s doesn't have expected prefix", obj.Key)
+					}
+				}
+			},
+			cleanup: func() {
+				cleanupTestFiles(t, s3, os.Getenv("AWS_S3_BUCKET"), []string{
+					"documents/file1.txt",
+					"documents/file2.txt",
+					"images/image1.jpg",
+					"images/image2.jpg",
+				})
+			},
+		},
+		{
+			name: "Delimiter Grouping",
+			setup: func() {
+				uploadTestFiles(t, s3, os.Getenv("AWS_S3_BUCKET"), []string{
+					"documents/important/file1.txt",
+					"documents/backup/file2.txt",
+					"images/landscape/image1.jpg",
+					"images/portrait/image2.jpg",
+				})
+			},
+			input: ListInput{
+				Bucket:    os.Getenv("AWS_S3_BUCKET"),
+				Delimiter: "/",
+				Prefix:    "documents/",
+			},
+			validate: func(result ListResponse, err error) {
+				if err != nil {
+					t.Fatalf("Expected no error, got %v", err)
+				}
+				// Should return common prefixes instead of individual files
+				if len(result.CommonPrefixes) != 2 {
+					t.Errorf("Expected 2 common prefixes, got %d", len(result.CommonPrefixes))
+				}
+			},
+			cleanup: func() {
+				cleanupTestFiles(t, s3, os.Getenv("AWS_S3_BUCKET"), []string{
+					"documents/important/file1.txt",
+					"documents/backup/file2.txt",
+					"images/landscape/image1.jpg",
+					"images/portrait/image2.jpg",
+				})
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.setup != nil {
+				tt.setup()
+			}
+
+			result, err := s3.List(tt.input)
+
+			if tt.validate != nil {
+				tt.validate(result, err)
+			}
+
+			if tt.cleanup != nil {
+				tt.cleanup()
+			}
+		})
+	}
+}
+
+// Helper functions
+func uploadTestFiles(t *testing.T, s3 *S3, bucket string, filenames []string) {
+	for _, filename := range filenames {
+		content := strings.NewReader("test content for " + filename)
+		_, err := s3.FilePut(UploadInput{
+			Bucket:      bucket,
+			ObjectKey:   filename,
+			ContentType: "text/plain",
+			Body:        content,
+		})
+		if err != nil {
+			t.Fatalf("Failed to upload test file %s: %v", filename, err)
+		}
+	}
+}
+
+func cleanupTestFiles(t *testing.T, s3 *S3, bucket string, filenames []string) {
+	for _, filename := range filenames {
+		err := s3.FileDelete(DeleteInput{
+			Bucket:    bucket,
+			ObjectKey: filename,
+		})
+		if err != nil {
+			t.Logf("Failed to cleanup test file %s: %v", filename, err)
+		}
+	}
+}