返回：<Promise>
¥Returns: <Promise>
异步地关闭目录的底层资源句柄。后续读取将导致错误。
¥Asynchronously close the directory's underlying resource handle. Subsequent reads will result in errors.
返回将在资源关闭后解决的 promise。
¥A promise is returned that will be resolved after the resource has been closed.