net / http.Request.URL.Host返回空字符串

Question

I was trying to redirect my client to https url. And I tried this:

func index(w http.ResponseWriter, r *http.Request) {
        if r.URL.Scheme != "https" {
                http.Redirect(w, r, "https://"+r.URL.Host+r.URL.Path, 301)
                return
        }
//....
}

But it gave me this response:

$ curl -i http://localhost
HTTP/1.1 301 Moved Permanently
Content-Type: text/html; charset=utf-8
Location: https:///
Date: Sat, 24 Nov 2018 20:02:33 GMT
Content-Length: 44

<a href="https:///">Moved Permanently</a>.

The mysterious thing is Location: https:/// this line. And I read the go doc again and found:

// URL specifies either the URI being requested (for server
// requests) or the URL to access (for client requests).
//
// For server requests the URL is parsed from the URI
// supplied on the Request-Line as stored in RequestURI.  **For
// most requests, fields other than Path and RawQuery will be
// empty. (See RFC 7230, Section 5.3)**
//
// For client requests, the URL's Host specifies the server to
// connect to, while the Request's Host field optionally
// specifies the Host header value to send in the HTTP
// request.
URL *url.URL

Then I've understood that why it's returning and empty string for r.URL.Host.

I have also tried r.Header.Get("Host") and then r.Header.Get("Origin"). It also gave me an empty string.

Any other way to get the host name?

Answer 1

Try using r.Host?

The docs say:

// For server requests Host specifies the host on which the URL
// is sought. Per RFC 7230, section 5.4, this is either the value
// of the "Host" header or the host name given in the URL itself.

So Maybe try that?

func index(w http.ResponseWriter, r *http.Request) {
    if r.URL.Scheme != "https" {
            http.Redirect(w, r, "https://"+r.Host+r.URL.Path, 301)
            return
    }
//....
}