if res.StatusCode/100 == 3 {
		newURL, err := res.Location()
		if err != nil {
			return fmt.Errorf("resolving redirect: %v", err)
		}
		if !strings.HasPrefix(newURL.String(), *root) {
			// Skip off-site redirects.
			return nil
		}
		crawl(newURL.String(), url)
		return nil
	}
	if res.StatusCode != 200 {
		return errors.New(res.Status)
	}
	slurp, err := io.ReadAll(res.Body)
	res.Body.Close()