code: func (c *cache) remove(key string) {
  	if cached, ok := c.items[key]; ok {
  		delete(c.items, key)
  		c.size -= cached.item.Size()
  		c.keyList.Remove(cached.element)
  	}
  }
docs: // Remove the item associated with the given key.
  // The caller should hold the cache lock.