Navigator operation requested with a context that does not include a Navigator in flutter web

I was just put official Doc code for see how Navigation work in web(chrome). But when I click button I get an error-> Navigator operation requested with a context that does not include a Navigator.

code->

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('First Route'),
        ),
        body: Center(
          child: ElevatedButton(
              child: Text('Open route'),
              // Within the `FirstRoute` widget
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => SecondRoute()),
                );
              }),
        ),
      ),
    );
  }
}

class SecondRoute extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Second Route"),
      ),
      body: Center(
        child: ElevatedButton(
          // Within the SecondRoute widget
          onPressed: () {
            Navigator.pop(context);
          },
          child: Text('Go back!'),
        ),
      ),
    );
  }
}

Thanks...