golang 强制对特定 ip 的 http 请求(类似于 curl --resolve)

func main() {
    dialer := &net.Dialer{
        Timeout:   30 * time.Second,
        KeepAlive: 30 * time.Second,
        // DualStack: true, // this is deprecated as of go 1.16
    }
    // or create your own transport, there's an example on godoc.
    http.DefaultTransport.(*http.Transport).DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {
        if addr == "google.com:443" {
            addr = "216.58.198.206:443"
        }
        return dialer.DialContext(ctx, network, addr)
    }
    resp, err := http.Get("https://google.com")
    log.Println(resp.Header, err)