writeStream.close([callback])
callback<Function>err<Error>
关闭 writeStream。可选择接受一个回调函数，该回调函数将在 writeStream 关闭后执行。
【Closes writeStream. Optionally accepts a
callback that will be executed once the writeStream
is closed.】
callback <Function>
err <Error>关闭 writeStream。可选择接受一个回调函数，该回调函数将在 writeStream 关闭后执行。
【Closes writeStream. Optionally accepts a
callback that will be executed once the writeStream
is closed.】