func waitForHTTPStream(respBody io.ReadCloser, w io.Writer) error {
	var tmp [1]byte
	// 8K copy buffer, reused for less allocs...
	bufp := poolBuf8k.Get()
	buf := *bufp
	defer poolBuf8k.Put(bufp)

	for {
		_, err := io.ReadFull(respBody, tmp[:])
		if err != nil {
			return err
		}
		// Check if we have a response ready or a filler byte.
		switch tmp[0] {