code: func (s *SkipList) Range(from, to interface{}) Iterator {
  	start := s.getPath(s.header, nil, from)
  	return &rangeIterator{
  		iter: iter{
  			current: &node{
  				forward:  []*node{start},
  				backward: start,
  			},
  			list: s,
  		},
  		upperLimit: to,
  		lowerLimit: from,
  	}
  }
docs: // Range returns an iterator that will go through all the
  // elements of the skip list that are greater or equal than from, but
  // less than to.