ParallelDownload does not close output file after download completed and merged?

[ZHOUYue67]

The *os.File returned by getOutputFile() never seems to get closed in mergeFile(). Is this a bug, or I'm using this the wrong way?

（Windows平台）用了ParallelDownload后立马os.Rename()文件会失败，提示文件正在被使用，我把parallel_download.go单独拿出来改，在mergeFile()里加上等同于defer file.Close()的代码，就可以正确使用了。
虽然os/file_windows.go的newFile()里，存在runtime.SetFinalizer(f.file, (*file).close)，但还是建议可控环境下主动调用os.File.Close()