code: func copyBuf(w io.Writer, r io.Reader) (int64, error) {
  	buf := buffer32KPool.Get().([]byte)
  	written, err := io.CopyBuffer(w, r, buf)
  	buffer32KPool.Put(buf)
  	return written, err
  }
docs: // copyBuf uses a shared buffer pool with io.CopyBuffer