func NewReadWriter(rw io.ReadWriter) ReadWriter {
	return &readWriter{r: rw, w: rw}
}
func NewReadWriter(rw io.ReadWriter) ReadWriter {
	return &readWriter{r: rw, w: rw}
}
func NewReadWriter ( rw io . ReadWriter ) ReadWriter { return & readWriter { r : rw , w : rw } }
// NewReadWriter returns a new ReadWriter with rw as both its source and its sink.
NewReadWriter returns a new ReadWriter with rw as both its source and its sink .