Address easy golint comments

tracker/memory/conn.go

@@ -210,7 +210,7 @@ func (c *Conn) PurgeInactivePeers(purgeEmptyTorrents bool, before time.Time) err
 	index := 0
 	keys := make([]string, len(c.torrents))
 
-	for infohash, _ := range c.torrents {
+	for infohash := range c.torrents {
 		keys[index] = infohash
 		index++
 	}

tracker/models/models.go

@@ -61,9 +61,9 @@ type PeerKey string
 func NewPeerKey(peerID string, ipv6 bool) PeerKey {
 	if ipv6 {
 		return PeerKey("6:" + peerID)
-	} else {
-		return PeerKey("4:" + peerID)
 	}
+
+	return PeerKey("4:" + peerID)
 }
 
 // PeerMap is a map from PeerKeys to Peers.