https://github.com/knative-extensions/eventing-github/blob/f34a508f89e52fe4ebd5eba5f630a0ae07d923cb/pkg/mtadapter/router/router.go#L54-L90

router.go

// ServeHTTP implements http.Handler.
func (h *Router) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	// Path-based dispatch
	h.routersMu.RLock()
	keyedHandler, ok := h.routers[r.URL.Path]
	h.routersMu.RUnlock()

	if ok {
		// Check if source still exists.
		_, err := h.lister.GitHubSources(keyedHandler.namespace).Get(keyedHandler.name)
		if err == nil {
			keyedHandler.handler.ServeHTTP(w, r)
			return
		}

		h.Unregister(r.URL.Path)
	}
	http.NotFoundHandler().ServeHTTP(w, r)
}

// Register adds a new GitHub event handler for the given GitHubSource.
func (h *Router) Register(name, namespace, path string, handler http.Handler) {
	h.routersMu.Lock()
	defer h.routersMu.Unlock()
	h.routers[path] = keyedHandler{
		handler:   handler,
		namespace: namespace,
		name:      name,
	}
}

// Unregister removes the GitHubSource served at the given path.
func (h *Router) Unregister(path string) {
	h.routersMu.Lock()
	defer h.routersMu.Unlock()
	delete(h.routers, path)
}