custom not found

router.go

@@ -6,12 +6,14 @@ import (
 )
 
 type Router struct {
-	t *tree
+	t        *tree
+	NotFound http.HandlerFunc
 }
 
 func New() *Router {
 	return &Router{
-		t: newTree(),
+		t:        newTree(),
+		NotFound: http.NotFound,
 	}
 }
 
@@ -22,7 +24,7 @@ func (rt *Router) Add(path string, foo http.HandlerFunc) error {
 func (rt *Router) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	foo := rt.t.Lookup(r.URL.Path)
 	if foo == nil {
-		http.NotFound(w, r)
+		rt.NotFound(w, r)
 		return
 	}
 	foo(w, r)