如何检测重定向是否被调用

Question

我有以下代码

package main

import (

    "log"

    "net/http"

)

func fooHandler(w http.ResponseWriter, r *http.Request) {

    // Here an if condition, if should redirect or not

    http.Redirect(w, r, "http://www.google.com", 301)

    // Do something....

    // Call function if redirect was invoked

}

func main() {

    http.HandleFunc("/", fooHandler)

    err := http.ListenAndServe(":9090", nil)

    if err != nil {

        log.Fatal("ListenAndServe: ", err)

    }

}

如何检测重定向是否写在响应对象中？