code: func (l *lagLogger) Min() int {
  	if len(l.measurements) == 0 {
  		return -1
  	}
  	min := int(l.measurements[0].highWaterMark - l.measurements[0].readOffset)
  	for _, m := range l.measurements[1:] {
  		lag := int(m.highWaterMark - m.readOffset)
  		if lag < min {
  			min = lag
  		}
  	}
  	return min
  }
docs: // Min returns the lowest lag seen (0 or positive) or -1 if no lags reported yet
  // note: values may be slightly out of date if negative values were reported
  // (see Store())