FutureBuilder

future.dart

import 'package:flutter/material.dart';
main() {    
    runApp(new TestSample());
}

class TestSample extends StatelessWidget{
    @override
    Widget build(BuildContext context) {
         var widget = new MaterialApp(
                home: new Scaffold(
                    body: new Center( 
                        child: new MyContainer(),
                    )
                ),
            );

            return widget;
        }
}

class MyContainer extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
        return new FutureBuilder<dynamic>(
            future: getWidgetText(),
            builder: (context, snapshot) {
                return new Text(snapshot.data);
            }
        );
    }

     getWidgetText() async {
        return "CHanges";
    }
}