https://github.com/knative-extensions/eventing-github/blob/f34a508f89e52fe4ebd5eba5f630a0ae07d923cb/pkg/common/handler.go#L54-L118

handler.go

func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	payload, err := h.Hook.Parse(r, ValidEvents...)
	if err != nil {
		if err == gh.ErrEventNotFound {
			w.WriteHeader(http.StatusNotFound)
			h.Logger.Info("Event not found")
			return
		}
		w.WriteHeader(http.StatusBadRequest)
		h.Logger.Errorf("Error processing request: %v", err)
		return
	}

	ctx := context.Background()
	if len(h.SinkURI) > 0 {
		ctx = cloudevents.ContextWithTarget(ctx, h.SinkURI)
	}

	err = h.handleEvent(ctx, payload, r.Header)

	if err != nil {
		h.Logger.Errorf("Event handler error: %v", err)
		w.WriteHeader(400)
		w.Write([]byte(err.Error()))
		return
	}
	h.Logger.Infof("Event processed")
	w.WriteHeader(202)
	w.Write([]byte("accepted"))
}

func (h *Handler) handleEvent(ctx context.Context, payload interface{}, hdr http.Header) error {
	gitHubEventType := hdr.Get(GHHeaderEvent)
	if gitHubEventType == "" {
		return fmt.Errorf("%q header is not set", GHHeaderEvent)
	}
	eventID := hdr.Get(GHHeaderDelivery)
	if eventID == "" {
		return fmt.Errorf("%q header is not set", GHHeaderDelivery)
	}

	h.Logger.Infof("Handling %s", gitHubEventType)

	cloudEventType := sourcesv1alpha1.GitHubEventType(gitHubEventType)
	subject, extensions := SubjectAndExtensionsFromGitHubEvent(gh.Event(gitHubEventType), payload, h.Logger)

	event := cloudevents.NewEvent()
	event.SetID(eventID)
	event.SetType(cloudEventType)
	event.SetSource(h.Source)
	event.SetSubject(subject)
	for k, v := range extensions {
		event.SetExtension(k, v)
	}

	if err := event.SetData(cloudevents.ApplicationJSON, payload); err != nil {
		return fmt.Errorf("failed to marshal event data: %w", err)
	}

	result := h.Client.Send(ctx, event)
	if !cloudevents.IsACK(result) {
		return result
	}
	return nil
}