code: func (h *ResponseHeader) PeekBytes(key []byte) []byte {
  	h.bufKV.key = append(h.bufKV.key[:0], key...)
  	normalizeHeaderKey(h.bufKV.key, h.disableNormalizing)
  	return h.peek(h.bufKV.key)
  }
docs: // PeekBytes returns header value for the given key.
  //
  // Returned value is valid until the next call to ResponseHeader.
  // Do not store references to returned value. Make copies instead.