Duplicate messages regardless of msg.Ack()?

[tamis-laan]

I'm publishing to a subject using go and reading from the subject using python. Although I'm acknowledging messages using python after processing the messages are not removed from the queue and I'm reprocessing them again and again.

// Create the stream
stream, err := js.CreateOrUpdateStream(context.Background(), jetstream.StreamConfig{
	Name:              "mystream",
	Subjects:          []string{"mystream.jobs"},
	MaxMsgsPerSubject: 10,
	Discard:           jetstream.DiscardNew,
	Retention:         jetstream.WorkQueuePolicy,
})

# Subscribe to stream
sub = await js.subscribe("mystream.jobs", "workers")

while True:
    # Get the next message
    msg = await sub.next_msg(timeout=60)

    # ... do some processing ...
    
    # Acknowledge message
    await msg.ack()

Am I doing something wrong? Is there something I don't understand?