code: func (d *DiskStorer) ResetExpiry(key string) error {
  	if !validKey(key) {
  		return errNoSession{}
  	}
  
  	filePath := path.Join(d.folderPath, key)
  	nowTime := time.Now().UTC()
  
  	return os.Chtimes(filePath, nowTime, nowTime)
  }
docs: // ResetExpiry resets the expiry of the key