Flutter/Dart/firebase:: Error when trying to sign out - flutter

Question

Not sure why I am not able to sign out.
When I click a button on the app bar, see 'sign out',
I click it,
system then asks me to confirm to sign out, I click it.
then I get an error and I am not signed out,
The expected result should be signing out without an error
CODE SNIP::
class _NotesViewState extends State<NotesView> {
void _popupMenuActionsPressed(value) async {
devtools.log('App bar $value was pressed');
switch (value) {
case MenuAction.logout:
final shouldLogout = await showLogOutDialog(context);
devtools.log('User logout');
if (shouldLogout) {
devtools.log('inside if statement');
await FirebaseAuth.instance.signOut();
Navigator.of(context)
.pushNamedAndRemoveUntil(homeRoute, (_) => false);
}
break;
default:
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Main UI'),
actions: [
PopupMenuButton<MenuAction>(
onSelected: (value) {
_popupMenuActionsPressed(value);
},
itemBuilder: (context) {
return [
const PopupMenuItem<MenuAction>(
value: MenuAction.logout,
child: Text('Sign out'),
)
];
},
)
],
),
body: const Text('Hello world'),
);
}
}
ERROR SNIP
User logout
[log] inside if statement
E/flutter (10193): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: [core/no-app] No Firebase App '[DEFAULT]' has been created - call Firebase.initializeApp()
E/flutter (10193): #0 MethodChannelFirebase.app
package:firebase_core_platform_interface/…/method_channel/method_channel_firebase.dart:193
E/flutter (10193): #1 Firebase.app
package:firebase_core/src/firebase.dart:56
E/flutter (10193): #2 FirebaseAuth.instance
package:firebase_auth/src/firebase_auth.dart:44
E/flutter (10193): #3 _NotesViewState._popupMenuActionsPressed
package:ijob_clone_app/main.dart:81
E/flutter (10193): <asynchronous suspension>
E/flutter (10193):

Answer 1

The error is not from the code, it is because you are not initializing firebase in your main function.
Edit your main function as follows:
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp();
runApp(myApp());
}

Answer 2

Go to your main.dart file and in the main function, you have to initialize Firebase first before you can use any of its services:
void main() async {
await Firebase.initializeApp();
...
runApp(your_widget_here);
}