Function as child containing state

main.dart

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    var auth = new Auth();

    return MaterialApp(
        title: 'Pod',
        debugShowCheckedModeBanner: false,
        theme: ThemeData(primarySwatch: Colors.amber),
        home: WithAuth(auth: auth, builder: (user) => DummyRootPage()));
  }
}

class DummyRootPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(),
        drawer: Drawer(
          child: Text("drawer"),
        ),
        body: Text('body'));
  }
}