add persistent volume

player.go

@@ -188,11 +188,17 @@ func (p *Player) Play() {
 // volume up and volume down using -0.5 or +0.5
 func (p *Player) Volume(v float64) float64 {
 
+	// check if no songs playing currently
 	if p._volume == nil {
 		p.volume += v
 		return p.volume
 	}
 
+	defer func() {
+		volume := int(p.volume*10) + 50
+		viper.Set("volume", volume)
+	}()
+
 	speaker.Lock()
 	p._volume.Volume += v
 	p.volume = p._volume.Volume

start.go

@@ -182,6 +182,10 @@ func start(application *tview.Application) {
 					appLog(err)
 				}
 
+				if err := viper.WriteConfig(); err != nil {
+					appLog(err)
+				}
+
 				application.Stop()
 
 			})