我想添加操作图标到我的AppBar中，如此Flutter example所示
但是我使用go_flutter，在MaterialApp.router构造函数中看不到任何允许插入图标部件的属性。
这是我到目前为止的代码。我如何从这里添加动作图标？

class MyApp extends StatelessWidget {
    const MyApp({super.key});

    @override
    Widget build(BuildContext context) {
        return MaterialApp.router(
            title: 'My App',
            routerConfig: _router,
            debugShowCheckedModeBanner: false,
        );  
    }   
}

final GoRouter _router = GoRouter(routes: [
    GoRoute(path: '/', builder: ((context, state) => Loading())),
    GoRoute(name: 'error', path: '/error/:message/:statusCode', builder: (context, state) => CheckError(
        message: state.params['message']!,
        statusCode: state.params['statusCode']!
    )),
    GoRoute(name: 'home', path: '/home', builder: (context, state) {
            Map data = state.extra as Map;
            return Home(data: data);
        },
    ),
]);