Answers for "how to get current log in user username in firebase database in flutter"

getting uid of user firebase flutter

final FirebaseUser user = await auth.currentUser();
final userid = user.uid;

how to sign out user in flutter with firebase authentication

final FirebaseAuth _auth = FirebaseAuth.instance;

Future<void> _signOut() async {
    await _auth.signOut();
    await _googleSignIn.signOut();
  }