public void EnqueueBook(long bookId)
{
var message = new QueueMessage() { BookId = bookId };
var json = JsonConvert.SerializeObject(message);
_pub.Publish(_topicName, new[] { new PubsubMessage()
{
Data = Google.Protobuf.ByteString.CopyFromUtf8(json)
} });
}
// [END enqueuebook]