code: func (s *items) removeAt(index int) Item {
  	item := (*s)[index]
  	copy((*s)[index:], (*s)[index+1:])
  	(*s)[len(*s)-1] = nil
  	*s = (*s)[:len(*s)-1]
  	return item
  }
docs: // removeAt removes a value at a given index, pulling all subsequent values
  // back.