How telegraf download data using mqtt_consumer.go

I don’t see how telegraf download data using mqtt_consumer.go. Can someone explain me which part of code is responsible for that? I assume that maybe telegraf is not fast enough to download all data from my mqtt broker. Do you have idea how to debug that?

Telegraf uses the this library to use MQTT.
I’m not a programmer, so I just don’t know how it technically does it.

If telegraf is not fast enough you should see messages piling up in your queue, is that the case?