http - 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。我尝试了这个:

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://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>.

神秘的是Location: https:///这一行。我再次阅读了 go 文档，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

然后我就明白了为什么它返回 r.URL.Host 的空字符串。

我还尝试过r.Header.Get("Host")，然后尝试r.Header.Get("Origin")。它还给了我一个空字符串。

还有其他方法获取主机名吗？

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，使用 r.Host 而不是 r.Header.Get("Host")