mobile-app/lib/main.dart

import 'package:flutter/material.dart';
import 'app.dart';
import 'data/repository/authentication_repository.dart';

void main() {
  runApp(App(authenticationRepository: AuthenticationRepository()));
}

Future<dynamic> myBackgroundMessageHandler(Map<String, dynamic> message) {
  if (message.containsKey('data')) {
    // Handle data message
    final dynamic data = message['data'];
  }

  if (message.containsKey('notification')) {
    // Handle notification message
    final dynamic notification = message['notification'];
  }

  // Or do other work.
}