code: func FileDescriptorsLimit(limit int64) FileStoreOption {
  	return func(o *FileStoreOptions) error {
  		if limit < 0 {
  			return fmt.Errorf("file descriptor limit must be a positive number")
  		}
  		o.FileDescriptorsLimit = limit
  		return nil
  	}
  }
docs: // FileDescriptorsLimit is a soft limit hinting at FileStore to try to
  // limit the number of concurrent opened files to that limit.