Firebase Cloud Messaging in flutter function works but didn't receive notification

I want to send fcm notication to device but the problem is it's hitting api success fully but the push notification is not send to app.

 Future<bool> callOnFcmApiSendPushNotifications(
      Future<String> userToken, Message message) async {

    print(message.message);
    print(userToken);
    final postUrl = 'https://fcm.googleapis.com/fcm/send';
    final data = {
      "notification": {"body": message.message, "title": "New Notification"},
      "priority": "high",
      "data": {
        "click_action": "FLUTTER_NOTIFICATION_CLICK",
        "id": "1",
        "status": "done"
      },
      "to": "$userToken"
    };

    final headers = {
      'content-type': 'application/json',
      'Authorization':
          'key=Server key'
    };

    print('hit till response');

    final response = await Dio()
        .post(postUrl, data: data, options: Options(headers: headers));
    print(response.statusCode);
    if (response.statusCode == 200) {
      // on success do sth
      print('test ok push CFM');
      return true;
    } else {
      print(' CFM error');
      // on failure do sth
      return false;
    }
  }

  static Future<String> getToken(userId) async {
    final Firestore _db = Firestore.instance;

    var token;
    await _db
        .collection('users')
        .document(userId)
        .collection('tokens')
        .getDocuments()
        .then((snapshot) {
      snapshot.documents.forEach((doc) {
        token = doc.documentID;
      });
    });

    return token;
  }

my message sending code

Future<void> addMessageToDb(
      Message message, User sender, User receiver) async {
    var map = message.toMap();

    await firestore
        .collection("messages")
        .document(message.senderId)
        .collection(message.receiverId)
        .add(map);

    var token = getToken(message.receiverId);
    print('token setted for fcm');
    callOnFcmApiSendPushNotifications(token, message);
    print('fcm worked');

    return await firestore
        .collection("messages")
        .document(message.receiverId)
        .collection(message.senderId)
        .add(map);
  }

my console after message is sent :

I/flutter (14894): hari
I/flutter (14894): token setted for fcm
I/flutter (14894): let's see
I/flutter (14894): Instance of 'Future<String>'
I/flutter (14894): hit till response
I/flutter (14894): fcm worked
I/flutter (14894): 200
I/flutter (14894): test ok push CFM

as in my console i can see all the print statement part fcm function but i do not get any notification in my app. Help appreciated