Flutter Realtime Database Problem

[ScienceTeo]

I have recently approached the world of flutter and now I have a problem, in practice I need to write info in a Realtime Database.

I created the void function (I've done the association final databaseReference = FirebaseDatabase.instance.reference(); before.

This is the function

void writeDB() async{
    User user = await _firebaseAuth.currentUser;
    FirebaseDatabase.instance.reference().child('user').equalTo(user.uid);
    await databaseReference.child('user').set({
      'email': FirebaseAuth.instance.currentUser.email,
      'name': "",
      'nick': "",
      "score": "0"
    });
  }

And this is the signIn function :

  Future<String> signIn(String email, String password) async {
    UserCredential result = await _firebaseAuth.signInWithEmailAndPassword(
        email: email, password: password);
      writeDB();
    User user = result.user;
    return user.uid;
  }

The registration and login system with firebase works fine, but the database is not written.

I also tried

  void writeDB() async{
    await databaseReference.child('user').set({
      "score": "0"
    });
  }

but it didn't work.

This is the Realtime DB config

{ "rules": { ".read": "true", ".write": "true" } }

Any help?