header.go
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)
}
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)
}
// 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.