Flutter项目自定义字体不生效问题求助

各位大佬好，我现在在Flutter项目里配置自定义字体遇到了问题，折腾半天字体还是没生效，想请大家帮忙看看哪里出问题了😭

我已经在pubspec.yaml里定义了要使用的字体，并且把字体文件放到了项目的fonts目录下，配置内容如下：

name: your_flutter_app
description: A new Flutter project
environment:
  sdk: ">=2.12.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter
  math_expressions: ^2.0.0  # Add this line to include the math_expressions package
flutter:
 fonts:
   - family: My-font
     fonts:
       - asset: fonts/Yarndings20Charted-regular.ttf

这是我的main.dart代码，已经在Text的样式里指定了这个自定义字体：

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(
  home: Scaffold (
    appBar: AppBar(
      title: Text('my First App'),
      centerTitle: true,
      backgroundColor: Colors.amber.shade100,
    ),
    body: Center(
      child: Text(
          'I am  Haroon',
        style: TextStyle(
            fontSize: 20,
            color: Colors.green,
            fontFamily: 'My-font',
        ),
      ),
    ),
    floatingActionButton: FloatingActionButton(
      child: Text('click'),
      onPressed: () {
        //Something Here;
      },
      backgroundColor: Colors.green,
    ),
  ),
));

我已经执行了flutter pub get更新依赖，但是字体还是没有生效，有没有大佬能帮我排查下问题呀？

备注：内容来源于stack exchange，提问作者هارون اخلاقی