Return PeerMap by reference.

In accordance with `go vet`, locks should only be returned by reference.

tracker/models/models.go

@@ -96,8 +96,8 @@ type Torrent struct {
 	ID       uint64 `json:"id"`
 	Infohash string `json:"infohash"`
 
-	Seeders  PeerMap `json:"seeders"`
-	Leechers PeerMap `json:"leechers"`
+	Seeders  *PeerMap `json:"seeders"`
+	Leechers *PeerMap `json:"leechers"`
 
 	Snatches       uint64  `json:"snatches"`
 	UpMultiplier   float64 `json:"up_multiplier"`

tracker/models/peermap.go

@@ -24,8 +24,8 @@ type PeerMap struct {
 }
 
 // NewPeerMap initializes the map for a new PeerMap.
-func NewPeerMap(seeders bool, cfg *config.Config) PeerMap {
-	pm := PeerMap{
+func NewPeerMap(seeders bool, cfg *config.Config) *PeerMap {
+	pm := &PeerMap{
 		Peers:   make(map[string]map[PeerKey]Peer),
 		Seeders: seeders,
 		Config:  cfg.NetConfig.SubnetConfig,