how to use pause animation in flutter

import 'package:flutter/material.dart';

void main(){
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyHomePage()
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage>
    with SingleTickerProviderStateMixin {
  AnimationController animationController;
  Animation<double> animation;
  bool _isPlaying = true;

  @override
  void initState() {
    super.initState();
    animationController = AnimationController(
      vsync: this,
      duration: Duration(seconds: 5),
    )
      ..addListener(() => setState(() {}))
      ..repeat();
    animation = Tween<double>(
      begin: 50.0,
      end: 120.0,
    ).animate(animationController);

    animationController.forward();
  }

  @override
  void dispose() {
    animationController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.black,
      appBar: AppBar(
        backgroundColor: Colors.red[700],
          title: Text("Pause Animation")),
      body: Column(
        children: <Widget>[
          Expanded(
            child: Center(
              child: Container(
                height: animation.value,
                width: animation.value,
                child: FlutterLogo(),
              ),
            ),
          ),
          RaisedButton(
              child: Text(_isPlaying ? "Pause Animation" : "Play Animation",style: TextStyle(color: Colors.white),),
              color: Colors.red[700],
              onPressed: () {
                _isPlaying
                    ? animationController.reset()
                    : animationController.repeat();
              }),
        ],
      ),
    );
  }
}