✅ make function sleep without freezing ui avalonia

public void LoginScreen()
{
    var vm = new LoginViewModel();

    Observable.Merge(
        vm.Ok,
        vm.Cancel
        .Select(_ => (UserModel?)null))
        .Take(1)
        .Subscribe(model =>
        {
            if (model != null)
            {
                LoggedInUser.Username = model.Username;
            }
            else
            {
                Environment.Exit(0);
            }
        });

    Content = vm;
}