How to reliably wait for a message to get sent?

[mwuertinger]

I have a simple application that just sends one single message and then terminates:

func main() {
    cli = ...

    err = cli.Publish(&client.PublishOptions{
        QoS: mqtt.QoS2,
        TopicName: []byte("foo/bar"),
        Message:   []byte("test"),
    })
    if err != nil {
        log.Fatalf("publish failed: %v", err)
    }
}

Unfortunately the message never gets sent although Publish returns nil. The reason for this behavior is the asynchronous message processing within the library.

Is there any way to reliably wait for a message to get sent?

I could imagine that initializing the cli.conn.send channel with a capacity of 0 (ie. setting sendBufSize = 0) could resolve the issue but I wanted to ask here first whether this is the right approach.

[skx]

As per the referenced issue above I am also encountering the same issue.

I have come up with a horrid solution which does work:

• Connect to MQ
• Subscribe to the topic you're going to publish upon
• Publish the message to the topic
  • Await the message reception - via the subscription
  • Sleep a while until this happens.
• Then unsubscribe
• And terminate.

Not ideal, but it has stood up to repeated testing.

mq.go.txt