/// <summary>
        /// Checks the current <see cref="HttpClient"/> and replaces it if headers or <see cref="Handler"/> has been modified
        /// </summary>
        protected (HttpClient Client, IDisposable Lock) GetClient()
        {
            // return current client if there are no changes
            var resetLevel = Interlocked.Exchange(ref _clientAdjustmentRequestSignal, 0);

            if (resetLevel > 0)
            {
                // block all reads and let all current requests finish
                using (_lock.WriterLock())
                {
                    // only reset the client if the handler has changed (signal = 2)
                    var resetClient = resetLevel == 2;

                    if (resetClient)
                    {
                        var handler = CreateHandler();

                        Client?.Dispose();
                        Client = handler != null ? new HttpClient(handler, true) : new HttpClient();
                    }

                    // apply new headers
                    Headers.ApplyTo(Client);

                    // allow the consumer to change the client
                    SetupClient(Client, resetClient);

                    // reset the state
                    Interlocked.Exchange(ref _clientAdjustmentRequestSignal, 0);
                }
            }

            return(Client, _lock.ReaderLock());
        }