header.go
func (h *RequestHeader) SetBytesKV(key, value []byte) {
	h.bufKV.key = append(h.bufKV.key[:0], key...)
	normalizeHeaderKey(h.bufKV.key, h.disableNormalizing)
	h.SetCanonical(h.bufKV.key, value)
}
func (h *RequestHeader) SetBytesKV(key, value []byte) {
	h.bufKV.key = append(h.bufKV.key[:0], key...)
	normalizeHeaderKey(h.bufKV.key, h.disableNormalizing)
	h.SetCanonical(h.bufKV.key, value)
}
// SetBytesKV sets the given 'key: value' header.
//
// Use AddBytesKV for setting multiple header values under the same key.