code: func (a *AddrManager) pickTried(bucket int) *list.Element {
  	var oldest *KnownAddress
  	var oldestElem *list.Element
  	for e := a.addrTried[bucket].Front(); e != nil; e = e.Next() {
  		ka := e.Value.(*KnownAddress)
  		if oldest == nil || oldest.na.Timestamp.After(ka.na.Timestamp) {
  			oldestElem = e
  			oldest = ka
  		}
  
  	}
  	return oldestElem
  }
docs: // pickTried selects an address from the tried bucket to be evicted.
  // We just choose the eldest. Bitcoind selects 4 random entries and throws away
  // the older of them.