code: func (c *Cache) Peek(key interface{}) (value interface{}, ok bool) {
  	c.lock.RLock()
  	value, ok = c.lru.Peek(key)
  	c.lock.RUnlock()
  	return value, ok
  }
docs: // Peek returns the key value (or undefined if not found) without updating
  // the "recently used"-ness of the key.