code: func (t *topicTable) leastRequested() *topicEntry {
  	for t.requested.Len() > 0 && t.topics[t.requested[0].topic] == nil {
  		heap.Pop(&t.requested)
  	}
  	if t.requested.Len() == 0 {
  		return nil
  	}
  	return t.topics[t.requested[0].topic].getFifoTail()
  }
docs: // removes least requested element from the fifo