code: func (q *poolEntryQueue) fetchOldest() *poolEntry {
  	if len(q.queue) == 0 {
  		return nil
  	}
  	for {
  		if e := q.queue[q.oldPtr]; e != nil {
  			delete(q.queue, q.oldPtr)
  			q.oldPtr++
  			return e
  		}
  		q.oldPtr++
  	}
  }
docs: // fetchOldest returns and removes the least recently accessed entry