咨询下GO复制这段代码如何获取进度呢

~~~ func copyFile(srcFileName string, dstFileName string) (written int64, err error) { srcFile, err := os.Open(srcFileName) if err != nil { fmt.Printf("open file error = %v\n", err) } defer srcFile.Close() //通过srcFile，获取到READER reader := bufio.NewReader(srcFile) //打开dstFileName dstFile, err := os.OpenFile(dstFileName, os.O_WRONLY|os.O_CREATE, 0666) if err != nil { fmt.Printf("open file error = %v\n", err) return } //通过dstFile，获取到WRITER writer := bufio.NewWriter(dstFile) //writer.Flush() defer dstFile.Close() return io.Copy(writer, reader) } ~~~