Update minimum required go version to 1.20 (#1161)

* Update CI to use go1.20, and use atomi.Int64

* Update go version in go.mod to go 1.20

* stringify the version name

.github/workflows/lint.yml

@@ -8,7 +8,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-go@v5
         with:
-          go-version: 1.19
+          go-version: "1.20"
           check-latest: true
       - uses: golangci/golangci-lint-action@v6
         with:

go.mod

@@ -1,6 +1,6 @@
 module github.com/lestrrat-go/jwx/v2
 
-go 1.19
+go 1.20
 
 require (
 	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.3.0

jwe/internal/aescbc/aescbc.go

@@ -19,21 +19,17 @@ const (
 
 const defaultBufSize int64 = 256 * 1024 * 1024
 
-// Grr, we would like to use atomic.Int64, but that's only available
-// from Go 1.19. Yes, we will cut support for Go 1.19 at some point,
-// but not today (probably going to up the minimum required Go version
-// some time after 1.22 is released)
-var maxBufSize int64
+var maxBufSize atomic.Int64
 
 func init() {
-	atomic.StoreInt64(&maxBufSize, defaultBufSize)
+	SetMaxBufferSize(defaultBufSize)
 }
 
 func SetMaxBufferSize(siz int64) {
 	if siz <= 0 {
 		siz = defaultBufSize
 	}
-	atomic.StoreInt64(&maxBufSize, siz)
+	maxBufSize.Store(siz)
 }
 
 func pad(buf []byte, n int) []byte {
@@ -43,7 +39,7 @@ func pad(buf []byte, n int) []byte {
 	}
 
 	bufsiz := len(buf) + rem
-	mbs := atomic.LoadInt64(&maxBufSize)
+	mbs := maxBufSize.Load()
 	if int64(bufsiz) > mbs {
 		panic(fmt.Errorf("failed to allocate buffer"))
 	}
@@ -200,7 +196,8 @@ func ensureSize(dst []byte, n int) []byte {
 func (c Hmac) Seal(dst, nonce, plaintext, data []byte) []byte {
 	ctlen := len(plaintext)
 	bufsiz := ctlen + c.Overhead()
-	mbs := atomic.LoadInt64(&maxBufSize)
+	mbs := maxBufSize.Load()
+
 	if int64(bufsiz) > mbs {
 		panic(fmt.Errorf("failed to allocate buffer"))
 	}