how to check 404 before execute ServeHTTP with goji

gistfile1.go

package main

import (
    "fmt"
    "github.com/zenazn/goji"
    "github.com/zenazn/goji/web"
    "net/http"
)

func main() {

    goji.Get("/hello/:name", hello)
    goji.Use(goji.DefaultMux.Router)
    goji.Use(Check)
    goji.Serve()
}

func hello(c web.C, w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hello, %s!", c.URLParams["name"])
}

func Check(c *web.C, h http.Handler) http.Handler {
    fn := func(w http.ResponseWriter, r *http.Request) {
        pattern := web.GetMatch(*c).Pattern
        if pattern != nil {
            fmt.Println("ok")
        } else {
            fmt.Println("404")
        }
        h.ServeHTTP(w, r)
    }
    return http.HandlerFunc(fn)
}