code: func GetFormat(in io.Reader) (*Format, error) {
  	var dec vorbis.Decoder
  	r := oggReader{source: in}
  	p, err := r.NextPacket()
  	if err != nil {
  		return nil, err
  	}
  	err = dec.ReadHeader(p)
  	if err != nil {
  		return nil, err
  	}
  	return &Format{
  		SampleRate: dec.SampleRate(),
  		Channels:   dec.Channels(),
  		Bitrate:    dec.Bitrate,
  	}, nil
  }
docs: // GetFormat reads the first ogg page from in to get the audio format.