all: bump go.mod version and drop compatibility shims

Also, remove the legacy import annotations.

Fixes golang/go#68147

Change-Id: Ibfcc9322f27224c0ba92ea42cd56912a7d8783fd
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/594256
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>

sha3/doc.go

@@ -59,4 +59,4 @@
 // They produce output of the same length, with the same security strengths
 // against all attacks. This means, in particular, that SHA3-256 only has
 // 128-bit collision resistance, because its output length is 32 bytes.
-package sha3 // import "golang.org/x/crypto/sha3"
+package sha3

sha3/hashes.go

@@ -9,6 +9,7 @@ package sha3
 // bytes.
 
 import (
+	"crypto"
 	"hash"
 )
 
@@ -40,6 +41,13 @@ func New512() hash.Hash {
 	return new512()
 }
 
+func init() {
+	crypto.RegisterHash(crypto.SHA3_224, New224)
+	crypto.RegisterHash(crypto.SHA3_256, New256)
+	crypto.RegisterHash(crypto.SHA3_384, New384)
+	crypto.RegisterHash(crypto.SHA3_512, New512)
+}
+
 func new224Generic() *state {
 	return &state{rate: 144, outputLen: 28, dsbyte: 0x06}
 }

sha3/register.go

@@ -1,18 +0,0 @@
-// Copyright 2014 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build go1.4
-
-package sha3
-
-import (
-	"crypto"
-)
-
-func init() {
-	crypto.RegisterHash(crypto.SHA3_224, New224)
-	crypto.RegisterHash(crypto.SHA3_256, New256)
-	crypto.RegisterHash(crypto.SHA3_384, New384)
-	crypto.RegisterHash(crypto.SHA3_512, New512)
-}