how to make an absolute path http redirect in golang

I was reading the source code goto, and I found the code below in goto/talk/0/main.go:

http.Redirect(w, r, url, http.StatusFound)

According to the context, url was an absolute path, and an absolute path redirect was expected. But as the golang/http/redirect mentioned:

> Redirect replies to the request with a redirect to url, which may be a path relative to the request path.

It results as a relative path redirect. I don't know if http.Redirect did an absolute path redirect before, but it doesn't nowadays.

So how can I make an absolute path redirect in golang?
I searched the Internet, but found nothing,can anyone help me?
Thanks in advance.

When you go to golang documentation for http.Redirect, you can actually click the blue colored header:

> func Redirect

It will bring you to the source code listing which is self-explanatory:

// Redirect replies to the request with a redirect to url,
// which may be a path relative to the request path.
func Redirect(w ResponseWriter, r *Request, urlStr string, code int) {
	if u, err := url.Parse(urlStr); err == nil {
		// If url was relative, make absolute by
		// combining with request path.
		// The browser would probably do this for us,
		// but doing it ourselves is more reliable.

		// NOTE(rsc): RFC 2616 says that the Location
		// line must be an absolute URI, like
		// "http://www.google.com/redirect/",
		// not a path like "/redirect/".
		// Unfortunately, we don't know what to
		// put in the host name section to get the
		// client to connect to us again, so we can't
		// know the right absolute URI to send back.
		// Because of this problem, no one pays attention
		// to the RFC; they all send back just a new path.
		// So do we.
		oldpath := r.URL.Path
		if oldpath == "" { // should not happen, but avoid a crash if it does
			oldpath = "/"
		}
		if u.Scheme == "" {
			// no leading http://server
			if urlStr == "" || urlStr[0] != '/' {
				// make relative path absolute
				olddir, _ := path.Split(oldpath)
				urlStr = olddir + urlStr
			}

			var query string
			if i := strings.Index(urlStr, "?"); i != -1 {
				urlStr, query = urlStr[:i], urlStr[i:]
			}

			// clean up but preserve trailing slash
			trailing := strings.HasSuffix(urlStr, "/")
			urlStr = path.Clean(urlStr)
			if trailing && !strings.HasSuffix(urlStr, "/") {
				urlStr += "/"
			}
			urlStr += query
		}
	}

	w.Header().Set("Location", urlStr)
	w.WriteHeader(code)

	// RFC2616 recommends that a short note "SHOULD" be included in the
	// response because older user agents may not understand 301/307.
	// Shouldn't send the response for POST or HEAD; that leaves GET.
	if r.Method == "GET" {
		note := "<a href=\"" + htmlEscape(urlStr) + "\">" + statusText[code] +
		        "</a>.\n"
		fmt.Fprintln(w, note)
	}
}

This trick applies to other functions as well.

I finally found that to perform an absolute path redirect, the url must be a complete url, such as http://www.stackoverflow.com or https://github.com, but not www.stackoverflow.com.