net/http.Request.URL.Host 返回空字符串

Question

我试图将我的客户端重定向到 https url。我试过这个：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        }//....}但它给了我这样的回应：$ curl -i http://localhostHTTP/1.1 301 Moved PermanentlyContent-Type: text/html; charset=utf-8Location: https:///Date: Sat, 24 Nov 2018 20:02:33 GMTContent-Length: 44<a href="https:///">Moved Permanently</a>.神秘的是Location: https:///这一行。我又看了一遍 go doc，发现：// 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然后我明白了为什么它返回和空字符串r.URL.Host。我也试过r.Header.Get("Host")然后r.Header.Get("Origin")。它还给了我一个空字符串。还有其他获取主机名的方法吗？

Answer 1

来自go doc http.request:

type Request struct {

        ...

        // For incoming requests, the Host header is promoted to the

        // Request.Host field and removed from the Header map.

       ...

        Header Header

       ...

        // For server requests Host specifies the host on which the

        // URL is sought. Per RFC 2616, this is either the value of

        // the "Host" header or the host name given in the URL itself.

        ...

        Host string

因此，r.Host不使用r.Header.Get("Host")

Answer 2

尝试使用 r.Host？

文档说：

// 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.

那么也许试试看？

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

    }

//....

}