fix(storage): retry net.OpError on connection reset (googleapis#10154)

We are seeing these errors surfaced via net.OpError as well as
url.Error. Update the ShouldRetry function accordingly.

Also, use net.ErrClosed sentinel over string matching.

Fixes googleapis#9478

storage/invoke.go

@@ -105,18 +105,16 @@ func ShouldRetry(err error) bool {
 	if errors.Is(err, io.ErrUnexpectedEOF) {
 		return true
 	}
+	if errors.Is(err, net.ErrClosed) {
+		return true
+	}
 
 	switch e := err.(type) {
-	case *net.OpError:
-		if strings.Contains(e.Error(), "use of closed network connection") {
-			// TODO: check against net.ErrClosed (go 1.16+) instead of string
-			return true
-		}
 	case *googleapi.Error:
 		// Retry on 408, 429, and 5xx, according to
 		// https://cloud.google.com/storage/docs/exponential-backoff.
 		return e.Code == 408 || e.Code == 429 || (e.Code >= 500 && e.Code < 600)
-	case *url.Error:
+	case *net.OpError, *url.Error:
 		// Retry socket-level errors ECONNREFUSED and ECONNRESET (from syscall).
 		// Unfortunately the error type is unexported, so we resort to string
 		// matching.

storage/invoke_test.go

@@ -346,6 +346,11 @@ func TestShouldRetry(t *testing.T) {
 			inputErr:    &url.Error{Op: "blah", URL: "blah", Err: errors.New("connection refused")},
 			shouldRetry: true,
 		},
+		{
+			desc:        "net.OpError{Err: errors.New(\"connection reset by peer\")}",
+			inputErr:    &net.OpError{Op: "blah", Net: "tcp", Err: errors.New("connection reset by peer")},
+			shouldRetry: true,
+		},
 		{
 			desc:        "io.ErrUnexpectedEOF",
 			inputErr:    io.ErrUnexpectedEOF,
@@ -382,9 +387,8 @@ func TestShouldRetry(t *testing.T) {
 			shouldRetry: false,
 		},
 		{
-			desc: "wrapped ErrClosed text",
-			// TODO: check directly against wrapped net.ErrClosed (go 1.16+)
-			inputErr:    &net.OpError{Op: "write", Err: errors.New("use of closed network connection")},
+			desc:        "wrapped net.ErrClosed",
+			inputErr:    &net.OpError{Err: net.ErrClosed},
 			shouldRetry: true,
 		},
 	} {