Fixed deadlock caused by misunderstanding of how defer works.

internal/radio/icecast.go

@@ -152,11 +152,11 @@ func IcecastWatchPlaylist(playlistPath string, lastNSongs int) error {
 			select {
 			case <-playlistFired:
 				lastPlayedCacheMutex.Lock()
-				defer lastPlayedCacheMutex.Unlock()
 				songs, err := lastPlayedSongs(lastNSongs, playlistPath)
 				if err == nil && len(songs) > 0 {
 					lastPlayedCache = songs
 				}
+				lastPlayedCacheMutex.Unlock()
 			}
 		}
 	}()