code: func (p *Parser) wavDuration() (time.Duration, error) {
  	if p.Size == 0 || p.AvgBytesPerSec == 0 {
  		return 0, fmt.Errorf("can't extract the duration due to the file not properly parsed")
  	}
  	duration := time.Duration((float64(p.Size) / float64(p.AvgBytesPerSec)) * float64(time.Second))
  	return duration, nil
  }
docs: // WavDuration returns the time duration of a wav container.