code: func (s *Cache) unsafeGet(key string) (*cacheItem, error) {
  	v, ok := s.values[key]
  	if !ok {
  		return nil, raiqub.InvalidKeyError(key)
  	}
  	return v, nil
  }
docs: // unsafeGet gets one cacheItem instance from its key without locking.
  //
  // Errors:
  // InvalidKeyError when requested key could not be found.