如何检测重定向是否被调用

Question

我有以下代码package mainimport (    "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？