header.go
func (h *RequestHeader) Header() []byte {
	h.bufKV.value = h.AppendBytes(h.bufKV.value[:0])
	return h.bufKV.value
}
func (h *RequestHeader) Header() []byte {
	h.bufKV.value = h.AppendBytes(h.bufKV.value[:0])
	return h.bufKV.value
}
// Header returns request header representation.
//
// The returned representation is valid until the next call to RequestHeader methods.