code: func (f *FreeList) freeNode(n *node) (out bool) {
  	f.mu.Lock()
  	if len(f.freelist) < cap(f.freelist) {
  		f.freelist = append(f.freelist, n)
  		out = true
  	}
  	f.mu.Unlock()
  	return
  }
docs: // freeNode adds the given node to the list, returning true if it was added
  // and false if it was discarded.