How I can get current active users from Firebase with Flutter?

I am making an application using flutter and firebase. I need to get active users from firebase. I am trying by creating a boolean field in firebase collection with name isActive = false and initiate a function with name _checkInternetConnectivity(); in this function I set when the internet connection is available update value of isActive = true in firebase and when there is no internet connection update value isActive = false so far my code is working perfectly but problem is that when internet connection is available it set the value of isActive = true but when there is no internet connection it unable to update the value isActive = false.
code is here:

void initState() {
    super.initState();
    _checkInternetConnectivity();
}

_checkInternetConnectivity() async {
    var connectivityResult = await (Connectivity().checkConnectivity());
    if (connectivityResult == ConnectivityResult.mobile) {
      FirebaseFirestore.instance.collection('Profile').doc(user.uid).update({
        'isActive': true,
      });
      print('done mobile');
    } else if (connectivityResult == ConnectivityResult.wifi) {
      _addData.doc(user.uid).update({
        'isActive': true,
      });
      print('done wifi');
    } else if (connectivityResult == ConnectivityResult.none) {
      FirebaseFirestore.instance.collection('Profile').doc(user.uid).update({
        'isActive': false,
      });
      print('done none');
    }
  }
}

so, how I can improve this code or any other way by which I can get active users from firebase with flutter.

Regards