code: func (l *labelIter) next() {
  	l.i++
  	if l.slice != nil {
  		if l.i >= len(l.slice) || l.i == len(l.slice)-1 && l.slice[l.i] == "" {
  			l.curStart = len(l.orig)
  		}
  	} else {
  		l.curStart = l.curEnd + 1
  		if l.curStart == len(l.orig)-1 && l.orig[l.curStart] == '.' {
  			l.curStart = len(l.orig)
  		}
  	}
  }
docs: // next sets the value to the next label. It skips the last label if it is empty.