Can listen to gong on the page

model/gong.go

@@ -66,6 +66,33 @@ func LoadGongs(cfg *config.Config) (gongs []*Gong, err error) {
 	return
 }
 
+func (g *Gong) Open() (*os.File, error) {
+	return os.Open(g.Path)
+}
+
+func (g *Gong) Size() (int64, error) {
+	if st, err := os.Stat(g.Path); err != nil {
+		return 0, err
+	} else {
+		return st.Size(), err
+	}
+}
+
+func (g *Gong) ContentType() string {
+	switch filepath.Ext(g.Path) {
+	case ".flac":
+		return "audio/flac"
+	case ".mp3":
+		return "audio/mpeg"
+	case ".ogg":
+		return "audio/ogg"
+	case ".wav":
+		return "audio/vnd.wav"
+	}
+
+	return "application/octet-stream"
+}
+
 func (g *Gong) Rename(newName string) error {
 	newPath := filepath.Join(filepath.Dir(g.Path), newName+filepath.Ext(g.Path))