code: func (s *VecStack) PeekN(n int) []*Vec {
  	var (
  		N   []*Vec
  		cur *item
  	)
  	N = make([]*Vec, 0, n)
  	cur = s.top
  	for len(N) < n {
  		if cur == nil {
  			break
  		}
  		N = append(N, cur.value)
  		cur = cur.next
  	}
  	return N
  }
docs: // PeekN returns at max the N topmost item without removing them from the stack.