* @param problem
     */
    public static <T> Result<T> addProblem(Result<T> result, ModelProblem problem) {
        return addProblems(result, Collections.singleton(problem));
    }

    /**
     * New result that includes the given
     *
     * @param result
     * @param problems
     */
    public static <T> Result<T> addProblems(Result<T> result, Iterable<? extends ModelProblem> problems) {

	wg.Add(1)
	go func() {
		urlq <- url
	}()
}

func addProblem(url, errmsg string) {
	msg := fmt.Sprintf("Error on %s: %s (from %s)", url, errmsg, linkSources[url])
	if *verbose {
		log.Print(msg)
	}
	problems = append(problems, msg)
}

func crawlLoop() {
	for url := range urlq {
		if err := doCrawl(url); err != nil {
			addProblem(url, err.Error())
		}
	}
}