title: Fcm background Notification in Flutter
body: <p>I have implemented a notification in the backgound with firebase messaging. But, the problem is this; how can I return the data from the function myBackgroundMessageHandler to FirebaseNotification? </p>
  
  <pre class="lang-dart prettyprint-override"><code>Future&lt;dynamic&gt; myBackgroundMessageHandler(Map&lt;String, dynamic&gt; message) {
        return Future&lt;void&gt;.value();
      }
  
      class FirebaseNotifications {
        FirebaseMessaging _firebaseMessaging;
        FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin;
  
        void setUpFirebase() {
          _firebaseMessaging = FirebaseMessaging();
        }
  
        void fcmListeners() {
          _firebaseMessaging.configure(
            onMessage: (Map&lt;String, dynamic&gt; message) async {
              print("OnMessage");
              processNotification(message);
              return;
            },
            onBackgroundMessage: myBackgroundMessageHandler,
            onLaunch: (Map&lt;String, dynamic&gt; message) async {
              print("onLaunch");
              processNotification(message);
              return;
            },
            onResume: (Map&lt;String, dynamic&gt; message) async {
              print("onResume");
              processNotification(message);
              return;
            },
          );
        }
  
        processNotification(message) {}
      }
  </code></pre>