example0

example0.dart

import 'package:flutter/material.dart';

void main() =>
    runApp(MaterialApp(home: Scaffold(body: Center(child: MyWidget()))));

Future<String> callAsyncFetch() =>
    Future.delayed(Duration(seconds: 3), () => "hi bro !");


class MyWidget extends StatelessWidget {
  @override
  Widget build(context) {
    callAsyncFetch().then((data) {
      return Text(data);  // doesn't work
    });
  }
}