Desafio da aplicação do Text.rich no texo "Oié, mundo Flutter"

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        // Application name
        title: 'Flutter Stateful Clicker Counter',
        theme: ThemeData(
          // Application theme data, you can set the colors for the application as
          // you want
          primarySwatch: Colors.blue,
        ),
        home: Scaffold(
            body: Text.rich(TextSpan(
                text: 'Oie',
                style: TextStyle(fontWeight: FontWeight.bold),
                children: [
              TextSpan(
                  text: ', mundo Flutter',
                  style: TextStyle(fontWeight: FontWeight.normal))
            ]))));
  }
}