Getting more detailed errors from FCM back-end service (#197)

Author: hiranya911

messaging/messaging.go

@@ -618,7 +618,9 @@ func (c *Client) makeSendRequest(ctx context.Context, req *fcmRequest) (string,
 		Method: http.MethodPost,
 		URL:    fmt.Sprintf("%s/projects/%s/messages:send", c.fcmEndpoint, c.project),
 		Body:   internal.NewJSONEntity(req),
+		Opts:   []internal.HTTPOption{internal.WithHeader("X-GOOG-API-FORMAT-VERSION", "2")},
 	}
+
 	resp, err := c.client.Do(ctx, request)
 	if err != nil {
 		return "", err

messaging/messaging_test.go

@@ -1020,6 +1020,9 @@ func checkFCMRequest(t *testing.T, b []byte, tr *http.Request, want map[string]i
 	if h := tr.Header.Get("Authorization"); h != "Bearer test-token" {
 		t.Errorf("Authorization = %q; want = %q", h, "Bearer test-token")
 	}
+	if h := tr.Header.Get("X-GOOG-API-FORMAT-VERSION"); h != "2" {
+		t.Errorf("X-GOOG-API-FORMAT-VERSION = %q; want = %q", h, "2")
+	}
 }
 
 func checkIIDRequest(t *testing.T, b []byte, tr *http.Request, op string) {