code: func (s *memcachedStorage) Set(key string, val interface{}, expires time.Duration) error {
  	item := &cachedItem{Val: val}
  	bytes, err := encodeGob(item)
  	if err != nil {
  		return err
  	}
  
  	var expiresInSeconds int64
  	if expires != 0 {
  		expiresInSeconds = int64(expires) / int64(time.Second)
  	}
  
  	memcachedItem := newItem(key, bytes, int32(expiresInSeconds))
  	return s.c.Set(memcachedItem)
  }
docs: // Set sets value to given key in the cache.