diff --git a/service/article/article.go b/service/article/article.go
index fe664c5..06dddf3 100644
--- a/service/article/article.go
+++ b/service/article/article.go
@@ -20,66 +20,62 @@ func (s Service) Wire(server *aicra.Server) {
 		s.DB.CreateTable(&model.Article{})
 	}
 
-	server.HandleFunc(http.MethodGet, "/articles", s.getAllArticles)
-	server.HandleFunc(http.MethodGet, "/user/{id}/articles", s.getArticlesByAuthor)
-	server.HandleFunc(http.MethodGet, "/article/{id}", s.getArticleByID)
-	server.HandleFunc(http.MethodPost, "/article", s.postArticle)
-	server.HandleFunc(http.MethodDelete, "/article/{id}", s.deleteArticle)
+	server.Handle(http.MethodGet, "/articles", s.getAllArticles)
+	server.Handle(http.MethodGet, "/user/{id}/articles", s.getArticlesByAuthor)
+	server.Handle(http.MethodGet, "/article/{id}", s.getArticleByID)
+	server.Handle(http.MethodPost, "/article", s.postArticle)
+	server.Handle(http.MethodDelete, "/article/{id}", s.deleteArticle)
 }
 
-func (s Service) getArticlesByAuthor(req api.Request, res *api.Response) {
+func (s Service) getArticlesByAuthor(req api.Request, res *api.Response) api.Error {
 	id, err := req.Param.GetUint("author_id")
 	if err != nil {
-		res.SetError(api.ErrorInvalidParam(), "author_id")
-		return
+		return api.ErrorInvalidParam
 	}
 	articles := make([]model.Article, 0)
 	s.DB.Where("author = ?", id).Find(&articles)
 	res.SetData("articles", articles)
-	res.SetError(api.ErrorSuccess())
+	return api.ErrorSuccess
 }
 
-func (s Service) getAllArticles(req api.Request, res *api.Response) {
+func (s Service) getAllArticles(req api.Request, res *api.Response) api.Error {
 	articles := make([]model.Article, 0)
 	s.DB.Find(&articles)
 	res.SetData("articles", articles)
-	res.SetError(api.ErrorSuccess())
+	return api.ErrorSuccess
 }
 
-func (s Service) getArticleByID(req api.Request, res *api.Response) {
+func (s Service) getArticleByID(req api.Request, res *api.Response) api.Error {
 	id, err := req.Param.GetUint("article_id")
 	if err != nil {
-		res.SetError(api.ErrorInvalidParam(), "article_id")
-		return
+		return api.ErrorInvalidParam
 	}
 
 	var article model.Article
 	if s.DB.First(&article, id).RecordNotFound() {
-		res.SetError(api.ErrorNoMatchFound())
-		return
+		return api.ErrorNoMatchFound
 	}
 
 	res.SetData("id", article.ID)
 	res.SetData("title", article.Title)
 	res.SetData("body", article.Body)
 	res.SetData("author", article.Author)
-	res.SetError(api.ErrorSuccess())
+	return api.ErrorSuccess
 }
 
-func (s Service) postArticle(req api.Request, res *api.Response) {
-
+func (s Service) postArticle(req api.Request, res *api.Response) api.Error {
+	return api.ErrorNotImplemented
 }
 
-func (s Service) deleteArticle(req api.Request, res *api.Response) {
+func (s Service) deleteArticle(req api.Request, res *api.Response) api.Error {
 	id, err := req.Param.GetUint("user_id")
 	if err != nil {
-		res.SetError(api.ErrorInvalidParam(), "user_id")
-		return
+		return api.ErrorInvalidParam
 	}
 
 	article := model.Article{}
 	article.ID = id
 	s.DB.Delete(&article)
 
-	res.SetError(api.ErrorSuccess())
+	return api.ErrorSuccess
 }
diff --git a/service/user/user.go b/service/user/user.go
index 6b5563d..6f7b14a 100644
--- a/service/user/user.go
+++ b/service/user/user.go
@@ -20,30 +20,28 @@ func (s Service) Wire(server *aicra.Server) {
 		s.DB.CreateTable(&model.User{})
 	}
 
-	server.HandleFunc(http.MethodGet, "/users", s.getAllUsers)
-	server.HandleFunc(http.MethodGet, "/user/{id}", s.getUserByID)
-	server.HandleFunc(http.MethodPost, "/user", s.createUser)
-	server.HandleFunc(http.MethodPut, "/user/{id}", s.updateUser)
-	server.HandleFunc(http.MethodDelete, "/user/{id}", s.deleteUser)
+	server.Handle(http.MethodGet, "/users", s.getAllUsers)
+	server.Handle(http.MethodGet, "/user/{id}", s.getUserByID)
+	server.Handle(http.MethodPost, "/user", s.createUser)
+	server.Handle(http.MethodPut, "/user/{id}", s.updateUser)
+	server.Handle(http.MethodDelete, "/user/{id}", s.deleteUser)
 }
 
-func (s Service) getAllUsers(req api.Request, res *api.Response) {
+func (s Service) getAllUsers(req api.Request, res *api.Response) api.Error {
 	users := make([]model.User, 0)
 	s.DB.Find(&users)
 	res.SetData("users", users)
-	res.SetError(api.ErrorSuccess())
+	return api.ErrorSuccess
 }
-func (s Service) getUserByID(req api.Request, res *api.Response) {
+func (s Service) getUserByID(req api.Request, res *api.Response) api.Error {
 	id, err := req.Param.GetUint("user_id")
 	if err != nil {
-		res.SetError(api.ErrorInvalidParam(), "user_id")
-		return
+		return api.ErrorInvalidParam
 	}
 
 	var user model.User
 	if s.DB.First(&user, id).RecordNotFound() {
-		res.SetError(api.ErrorNoMatchFound())
-		return
+		return api.ErrorNoMatchFound
 	}
 
 	res.SetData("id", user.ID)
@@ -51,32 +49,28 @@ func (s Service) getUserByID(req api.Request, res *api.Response) {
 	res.SetData("firstname", user.Firstname)
 	res.SetData("lastname", user.Lastname)
 	res.SetData("articles", user.Articles)
-	res.SetError(api.ErrorSuccess())
+	return api.ErrorSuccess
 }
 
-func (s Service) createUser(req api.Request, res *api.Response) {
+func (s Service) createUser(req api.Request, res *api.Response) api.Error {
 	var user model.User
 	var err error
 	user.Username, err = req.Param.GetString("username")
 	if err != nil {
-		res.SetError(api.ErrorInvalidParam(), "username")
-		return
+		return api.ErrorInvalidParam
 	}
 	user.Firstname, err = req.Param.GetString("firstname")
 	if err != nil {
-		res.SetError(api.ErrorInvalidParam(), "firstname")
-		return
+		return api.ErrorInvalidParam
 	}
 	user.Lastname, err = req.Param.GetString("lastname")
 	if err != nil {
-		res.SetError(api.ErrorInvalidParam(), "lastname")
-		return
+		return api.ErrorInvalidParam
 	}
 
 	s.DB.Create(&user)
 	if s.DB.Last(&user).RecordNotFound() {
-		res.SetError(api.ErrorNoMatchFound())
-		return
+		return api.ErrorNoMatchFound
 	}
 
 	res.SetData("id", user.ID)
@@ -84,20 +78,18 @@ func (s Service) createUser(req api.Request, res *api.Response) {
 	res.SetData("firstname", user.Firstname)
 	res.SetData("lastname", user.Lastname)
 	res.SetData("articles", user.Articles)
-	res.SetError(api.ErrorSuccess())
+	return api.ErrorSuccess
 }
 
-func (s Service) updateUser(req api.Request, res *api.Response) {
+func (s Service) updateUser(req api.Request, res *api.Response) api.Error {
 	id, err := req.Param.GetUint("user_id")
 	if err != nil {
-		res.SetError(api.ErrorInvalidParam(), "user_id")
-		return
+		return api.ErrorInvalidParam
 	}
 
 	var user model.User
 	if s.DB.First(&user, id).RecordNotFound() {
-		res.SetError(api.ErrorNoMatchFound())
-		return
+		return api.ErrorNoMatchFound
 	}
 
 	// override with updated values
@@ -113,21 +105,19 @@ func (s Service) updateUser(req api.Request, res *api.Response) {
 
 	// update
 	if s.DB.Save(&user).RowsAffected < 1 {
-		res.SetError(api.ErrorFailure())
-		return
+		return api.ErrorFailure
 	}
-	res.SetError(api.ErrorSuccess())
+	return api.ErrorSuccess
 }
 
-func (s Service) deleteUser(req api.Request, res *api.Response) {
+func (s Service) deleteUser(req api.Request, res *api.Response) api.Error {
 	id, err := req.Param.GetUint("user_id")
 	if err != nil {
-		res.SetError(api.ErrorInvalidParam(), "user_id")
-		return
+		return api.ErrorInvalidParam
 	}
 
 	user := model.User{}
 	user.ID = id
 	s.DB.Delete(&user)
-	res.SetError(api.ErrorSuccess())
+	return api.ErrorSuccess
 }