/// <summary>
 /// This method causes the communication listener to close. Close is a terminal state and
 ///             this method allows the communication listener to transition to this state in a
 ///             graceful manner.
 /// </summary>
 /// <param name="cancellationToken">Cancellation token</param>
 /// <returns>
 /// A <see cref="T:System.Threading.Tasks.Task">Task</see> that represents outstanding operation.
 /// </returns>
 protected override async Task CloseImplAsync(CancellationToken cancellationToken)
 {
     await ServiceBusClient.CloseAsync();
 }