监听多个端口：

func handler2(w http.ResponseWriter, r *http.Request) {    fmt.Fprintf(w, "Hello, HTTP Server1")}func handler1(w http.ResponseWriter, r *http.Request) {    fmt.Fprintf(w, "Hello, HTTP Server2")}func main() {    go func(){        mux := http.NewServeMux()        mux.HandleFunc("/", handler2)        http.ListenAndServe(":1234", mux)    }()    mux := http.NewServeMux()    mux.HandleFunc("/", handler1)    http.ListenAndServe(":12345", mux)}