code: func fmtEtimeDuration(d time.Duration) string {
  	days := d / (24 * time.Hour)
  	hours := d % (24 * time.Hour)
  	minutes := hours % time.Hour
  	seconds := math.Mod(minutes.Seconds(), 60)
  	var b bytes.Buffer
  	if days > 0 {
  		fmt.Fprintf(&b, "%02d-", days)
  	}
  	if hours/time.Hour > 0 {
  		fmt.Fprintf(&b, "%02d:", hours/time.Hour)
  	}
  	fmt.Fprintf(&b, "%02d:", minutes/time.Minute)
  	fmt.Fprintf(&b, "%02.0f", seconds)
  	return b.String()
  }
docs: // fmtEtimeDuration formats etime's duration based on ps' format:
  // [[DD-]hh:]mm:ss
  // format specification: http://linuxcommand.org/lc3_man_pages/ps1.html