[ERROR:flutter/lib/ui/ui_dart_state.cc(166)] Unhandled Exception: [core/no-app] No Firebase App '[DEFAULT]' has been created - call Firebase.initializeApp() code example

Example: [core/no-app] No Firebase App '[DEFAULT]' has been created - call Firebase.initializeApp() flutter

import 'package:firebase_core/firebase_core.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}