public override Task <Empty> Unsubscribe(Empty request, ServerCallContext context)
        {
            var contextLogin = context.GetLogin();

            _grpcObservable.Unregister(contextLogin);

            return(Task.FromResult(new Empty()));
        }
        public override async Task Notify(Empty request, IServerStreamWriter <proto.EventMessage> responseStream,
                                          ServerCallContext context)
        {
            var contextLogin = context.GetLogin();
            var subscriber   = new GrpcNotificationObserver(contextLogin, responseStream);

            _grpcObservable.Register(subscriber);

            while (!_grpcObservable.HasUserUnsubscribed(subscriber.Login) &&
                   !context.CancellationToken.IsCancellationRequested)
            {
                await Task.Delay(1000);
            }

            if (!context.CancellationToken.IsCancellationRequested)
            {
                _grpcObservable.Unregister(subscriber.Login);
            }
        }