if r.Host != "" {
		// Hostname is provided, so we can reasonably construct a URL.
		rawurl := r.Host + uriStr
		if r.TLS == nil {
			rawurl = "http://" + rawurl
		} else {
			rawurl = "https://" + rawurl
		}
		url, err := url.Parse(rawurl)
		if err != nil {
			return nil, errors.New("cgi: failed to parse host and REQUEST_URI into a URL: " + rawurl)
		}
		r.URL = url
	}