fix: Ensure trailing slash in CustomEndpoint is handled gracefully

simples3.go

@@ -189,6 +189,11 @@ func (s3 *S3) SetEndpoint(uri string) *S3 {
 		if !strings.HasPrefix(uri, "http") {
 			uri = "https://" + uri
 		}
+
+		// make sure there is no trailing slash
+		if uri[len(uri)-1] == '/' {
+			uri = uri[:len(uri)-1]
+		}
 		s3.Endpoint = uri
 	}
 	return s3

simples3_test.go

@@ -351,6 +351,12 @@ func TestCustomEndpoint(t *testing.T) {
 	if s3.getURL("bucket3") != "https://example.com/bucket3" {
 		t.Errorf("S3.SetEndpoint() got = %v", s3.Endpoint)
 	}
+
+	// try with trailing slash
+	s3.SetEndpoint("https://example.com/foobar/")
+	if s3.getURL("bucket4") != "https://example.com/foobar/bucket4" {
+		t.Errorf("S3.SetEndpoint() got = %v", s3.Endpoint)
+	}
 }
 
 func TestGetURL(t *testing.T) {