Dont lock the player list all the time when serving the GeoJSON over /players.

cmd/mtwebmapper/players.go

@@ -86,10 +86,12 @@ func (ps *players) run() {
 
 func (ps *players) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 	rw.Header().Set("Content-Type", "application/json")
+	var pls []*player
 	ps.mu.RLock()
-	defer ps.mu.RUnlock()
+	pls = ps.pls
+	ps.mu.RUnlock()
 	encoder := json.NewEncoder(rw)
-	if err := encoder.Encode(ps.pls); err != nil {
+	if err := encoder.Encode(pls); err != nil {
 		log.Printf("error: sending JSON failed: %s\n", err)
 	}
 }