dependencies:
     utopic_toast: ^0.1.3

import 'package:utopic_toast/utopic_toast.dart';

// wrap MaterialApp builder's child with ToastOverlay and set your custom params
MaterialApp(
  ...
  builder: (context, child) {
    return ToastOverlay(child: child);
  },
  ...
);

var toastFuture = ToastManager().showToast(
  'YOUR MESSAGE TO USER',
  type: ToastType.error, // set toast type to change presetted theme color 
  action: ToastAction(
    label: 'HAY',
    onPressed: (hideToastFn) {
      print('yay');
      hideToastFn();
    },
  ),
  duration: Duration(seconds: 3),
);

toastFuture.dismiss(); // to hide toast