code: func (i *Intervals) Last() (end uint64) {
  	i.mu.RLock()
  	defer i.mu.RUnlock()
  
  	l := len(i.ranges)
  	if l == 0 {
  		return 0
  	}
  	return i.ranges[l-1][1]
  }
docs: // Last returns the value that is at the end of the last interval.