Refine must2 and apply NewAesGcm() to all usage (#5011)

* Refine must2 and apply NewAesGcm() to all usage

* Remove unused package

* Fix test

common/common.go

@@ -23,7 +23,9 @@ func Must(err error) {
 }
 
 // Must2 panics if the second parameter is not nil, otherwise returns the first parameter.
-func Must2(v interface{}, err error) interface{} {
+// This is useful when function returned "sth, err" and avoid many "if err != nil"
+// Internal usage only, if user input can cause err, it must be handled
+func Must2[T any](v T, err error) T {
 	Must(err)
 	return v
 }

common/crypto/aes.go

@@ -32,9 +32,7 @@ func NewAesCTRStream(key []byte, iv []byte) cipher.Stream {
 
 // NewAesGcm creates a AEAD cipher based on AES-GCM.
 func NewAesGcm(key []byte) cipher.AEAD {
-	block, err := aes.NewCipher(key)
-	common.Must(err)
-	aead, err := cipher.NewGCM(block)
-	common.Must(err)
+	block := common.Must2(aes.NewCipher(key))
+	aead := common.Must2(cipher.NewGCM(block))
 	return aead
 }

common/crypto/auth_test.go

@@ -2,8 +2,6 @@ package crypto_test
 
 import (
 	"bytes"
-	"crypto/aes"
-	"crypto/cipher"
 	"crypto/rand"
 	"io"
 	"testing"
@@ -18,11 +16,8 @@ import (
 func TestAuthenticationReaderWriter(t *testing.T) {
 	key := make([]byte, 16)
 	rand.Read(key)
-	block, err := aes.NewCipher(key)
-	common.Must(err)
 
-	aead, err := cipher.NewGCM(block)
-	common.Must(err)
+	aead := NewAesGcm(key)
 
 	const payloadSize = 1024 * 80
 	rawPayload := make([]byte, payloadSize)
@@ -71,7 +66,7 @@ func TestAuthenticationReaderWriter(t *testing.T) {
 		t.Error(r)
 	}
 
-	_, err = reader.ReadMultiBuffer()
+	_, err := reader.ReadMultiBuffer()
 	if err != io.EOF {
 		t.Error("error: ", err)
 	}
@@ -80,11 +75,8 @@ func TestAuthenticationReaderWriter(t *testing.T) {
 func TestAuthenticationReaderWriterPacket(t *testing.T) {
 	key := make([]byte, 16)
 	common.Must2(rand.Read(key))
-	block, err := aes.NewCipher(key)
-	common.Must(err)
 
-	aead, err := cipher.NewGCM(block)
-	common.Must(err)
+	aead := NewAesGcm(key)
 
 	cache := buf.New()
 	iv := make([]byte, 12)