use a new thread safe map

internal/universal/head.go

@@ -43,8 +43,14 @@ func HandleHeadRequest(w http.ResponseWriter, r *http.Request, t *torrent.Torren
 	accessKey := segments[len(segments)-2]
 	filename := segments[len(segments)-1]
 
-	torrent, _ := t.TorrentMap.Get(accessKey)
-	if torrent == nil {
+	torrents, ok := t.DirectoryMap.Get(baseDirectory)
+	if !ok {
+		log.Warnf("Cannot find directory %s", baseDirectory)
+		http.Error(w, "File not found", http.StatusNotFound)
+		return
+	}
+	torrent, ok := torrents.Get(accessKey)
+	if !ok {
 		log.Warnf("Cannot find torrent %s in the directory %s", accessKey, baseDirectory)
 		http.Error(w, "File not found", http.StatusNotFound)
 		return