Golang net/http客户端 - 捕获提供响应的服务器的IP地址

Question

使用Golang(默认HTTP客户端),我无法直接确定处理请求的服务器的IP地址.例如,在请求example.com时,example.com在请求时解析的IP地址是多少？

import "net/http"

resp, err := http.Get("http://example.com/")

resp对象包含resp.RemoteAddr属性,但在客户端操作期间未使用如下所述.

 // RemoteAddr allows HTTP servers and other software to record
 // the network address that sent the request, usually for
 // logging. This field is not filled in by ReadRequest and
 // has no defined format. The HTTP server in this package
 // sets RemoteAddr to an "IP:port" address before invoking a
 // handler.
 // This field is ignored by the HTTP client.
 RemoteAddr string

有没有直接的方法来实现这一目标？我最初的想法是:

1. 启动对远程域的DNS查找
2. 使用返回的A/AAAA记录创建新的http传输
3. 提出要求
4. 在响应对象上设置RemoteAddr属性

有没有更好的办法？

谢谢.

更新 - 使用@flimzy的建议.此方法将远程IP:PORT存储到request.RemoteAddr属性中.我还添加了对多个重定向的支持,以便每个后续请求都填充了RemoteAddr.

request, _ := http.NewRequest("GET", "http://www.google.com", nil)
client := &http.Client{
    Transport:&http.Transport{
        DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
            conn, err := net.Dial(network, addr)
            request.RemoteAddr = conn.RemoteAddr().String()
            return conn, err
        },
    },
    CheckRedirect: func(req *http.Request, via []*http.Request) error {
        request = req
        return nil
    },
}
resp, _ := client.Do(request)

Answer 1

据我所知,使用标准库实现此目的的唯一方法是使用自定义http.Transport记录远程IP地址,例如在DialContext函数中.

client := &http.Client{
    Transport: &http.Transport{
        DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
            conn, err := net.Dial(network, addr)
            fmt.Printf("Remote IP: %s\n", conn.RemoteAddr())
            return conn, err
        },
    },
}
resp, _ := client.Get("http://www.google.com")

将连接IP与响应联系起来留给读者练习.