code: func (pool *serverPool) discoverNodes() {
  	ch := make(chan *discv5.Node)
  	go func() {
  		pool.server.DiscV5.SearchTopic(pool.topic, pool.discSetPeriod, ch, pool.discLookups)
  		close(ch)
  	}()
  	for n := range ch {
  		pubkey, err := decodePubkey64(n.ID[:])
  		if err != nil {
  			continue
  		}
  		pool.discNodes <- enode.NewV4(pubkey, n.IP, int(n.TCP), int(n.UDP))
  	}
  }
docs: // discoverNodes wraps SearchTopic, converting result nodes to enode.Node.