Fix context.DeadlineExceeded comparison (#1488)

internal/retry/retry.go

@@ -18,6 +18,7 @@ package retry
 
 import (
 	"context"
+	"errors"
 	"fmt"
 
 	"github.com/google/go-containerregistry/internal/retry/wait"
@@ -36,7 +37,7 @@ type temporary interface {
 
 // IsTemporary returns true if err implements Temporary() and it returns true.
 func IsTemporary(err error) bool {
-	if err == context.DeadlineExceeded {
+	if errors.Is(err, context.DeadlineExceeded) {
 		return false
 	}
 	if te, ok := err.(temporary); ok && te.Temporary() {

internal/retry/retry_test.go

@@ -17,6 +17,8 @@ package retry
 import (
 	"context"
 	"fmt"
+	"net/http"
+	"net/url"
 	"testing"
 )
 
@@ -55,6 +57,14 @@ func TestRetry(t *testing.T) {
 		predicate:   IsTemporary,
 		err:         context.DeadlineExceeded,
 		shouldRetry: false,
+	}, {
+		predicate: IsTemporary,
+		err: &url.Error{
+			Op:  http.MethodPost,
+			URL: "http://127.0.0.1:56520/v2/example/blobs/uploads/",
+			Err: context.DeadlineExceeded,
+		},
+		shouldRetry: false,
 	}} {
 		// Make sure we retry 5 times if we shouldRetry.
 		steps := 5