no sound. when i use, how i get the sound

[AiPacino]

overlay := ffmpeg.Input("./123.png")
err := ffmpeg.Filter(
	[]*ffmpeg.Stream{
		ffmpeg.Input("./1.mp4"),
		overlay,
	}, "overlay", ffmpeg.Args{"0:0"}).
	Output("./2.mp4").OverWriteOutput().ErrorToStdOut().Run()

if err != nil {
	log.Println(err)
}

[abellee]

overlay := ffmpeg.Input("./123.png")
err := ffmpeg.Filter(
	[]*ffmpeg.Stream{
		ffmpeg.Input("./1.mp4"),
		overlay,
	}, "overlay", ffmpeg.Args{"0:0"}).
	Output("./2.mp4", ffmpeg.KwArgs{"map": "0:a"}).OverWriteOutput().ErrorToStdOut().Run()

if err != nil {
	log.Println(err)
}