scaffold mess-anger flutter

import 'package:flutter/material.dart';

class MyBottomSheet extends StatelessWidget {
  var scaffoldKey = GlobalKey<ScaffoldState>();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: scaffoldKey,
      appBar: AppBar(
        title: Text("Snackbar"),
      ),
      body: Center(
        child: Container(
            color: Colors.white,
            child: ElevatedButton(
                onPressed: () {
                  var snackbar = SnackBar(
                    duration: Duration(minutes: 1),
                    backgroundColor: Colors.redAccent,
                    content: Text("You are messaged has deleted."),
                    action: SnackBarAction(label: "Undo", onPressed: () {}),
                  );
                  ScaffoldMessenger.of(context).showSnackBar(snackbar);
                  //Scaffold.of(context).showSnackBar(snackbar);
                },
                child: Text("Show SnackBar"))),
      ),
    );
  }
}