//	https://pkg.go.dev/net/http#example-ResponseWriter-Trailers
const TrailerPrefix = "Trailer:"

// finalTrailers is called after the Handler exits and returns a non-nil
// value if the Handler set any trailers.
func (w *response) finalTrailers() Header {
	var t Header
	for k, vv := range w.handlerHeader {
		if kk, found := strings.CutPrefix(k, TrailerPrefix); found {
			if t == nil {
				t = make(Header)
			}

			streamID:  rws.stream.id,
			h:         rws.handlerHeader,
			trailers:  rws.trailers,
			endStream: true,
		})
		return len(p), err
	}
	return len(p), nil
}

// TrailerPrefix is a magic prefix for ResponseWriter.Header map keys
// that, if present, signals that the map entry is actually for
// the response trailers, and not the response headers. The prefix