A flutter plugin provides the best way to exit the app doesn't call exit(0) in dart code.

add plugin to your pubspec.yaml

flutter_exit_app: release

• import plugin

import 'package:flutter_exit_app/flutter_exit_app.dart';

• call exit app static method

// call this to exit app
FlutterExitApp.exitApp();

for IOS if you need to force exit app set iosForceExit to true

// force exit in ios
FlutterExitApp.exitApp(iosForceExit: true);