handleSignOut static method
Implementation
static Future<Null> handleSignOut(BuildContext context) async {
await Firebase.initializeApp();
final GoogleSignIn googleSignIn = GoogleSignIn();
await FirebaseAuth.instance.signOut();
await googleSignIn.disconnect();
await googleSignIn.signOut();
Navigator.pushReplacement(
context, MaterialPageRoute(builder: (context) => LoginScreen()));
}