Tracker to store last processed event id

tracker.go

sub, err := sc.Subscribe("eventstore.events", func(m *stan.Msg) {
	// check if event was already processed
	if p.tracker.IsDuplicateOperation(p.name, event.ID) {
		log.WithFields(eventLogFields).WithFields(subLogFields).Trace("duplicate")
		if err := m.Ack(); err != nil {
			log.WithFields(eventLogFields).WithFields(subLogFields).WithError(err).Error("ack duplicate event")
		}
		return
	}
  
  	// your code
  
  	// track event as processed
	if err := r.tracker.ProcessingEvent(r.name, event.ID); err != nil {
		log.WithFields(eventLogFields).WithFields(r.baseLogFields).WithError(err).Error("track event as processed")
	}
	// ack message
	if err := m.Ack(); err != nil {
		log.WithFields(eventLogFields).WithFields(r.baseLogFields).WithError(err).Error("ack event")
	}
},
  stan.maxInFlight(1),
  stan.AckWait("30s"),
  stan.SetManualAckMode(),
  stan.DurableName(durableName),
)