fix FcmErrorCode error type (#192)

* fix FcmErrorCode error type

* update changelog

Author: chemidy

CHANGELOG.md

@@ -1,5 +1,7 @@
 # Unreleased
 
+- [fixed] Fixing error handling in FCM. The SDK now checks the key 
+  `type.googleapis.com/google.firebase.fcm.v1.FcmError` to set error code.
 - [added] `messaging.ApsAlert` type now supports subtitle in its payload.
 
 # v3.4.0

messaging/messaging.go

@@ -633,7 +633,7 @@ func (c *Client) makeSendRequest(ctx context.Context, req *fcmRequest) (string,
 	json.Unmarshal(resp.Body, &fe) // ignore any json parse errors at this level
 	var serverCode string
 	for _, d := range fe.Error.Details {
-		if d.Type == "type.googleapis.com/google.firebase.fcm.v1.FcmErrorCode" {
+		if d.Type == "type.googleapis.com/google.firebase.fcm.v1.FcmError" {
 			serverCode = d.ErrorCode
 			break
 		}

messaging/messaging_test.go

@@ -812,7 +812,7 @@ func TestSendError(t *testing.T) {
 		},
 		{
 			resp: `{"error": {"status": "INVALID_ARGUMENT", "message": "test error", "details": [` +
-				`{"@type": "type.googleapis.com/google.firebase.fcm.v1.FcmErrorCode", "errorCode": "UNREGISTERED"}]}}`,
+				`{"@type": "type.googleapis.com/google.firebase.fcm.v1.FcmError", "errorCode": "UNREGISTERED"}]}}`,
 			want: "http error status: 500; reason: app instance has been unregistered; code: registration-token-not-registered; " +
 				"details: test error",
 			check: IsRegistrationTokenNotRegistered,