mux.Vars unable to read url

[Gubaz311]

i have struct

type Server struct {
	DB     *gorm.DB
	Router *mux.Router
}

and the struct have func:

func (s *Server) StartApi() {

	s.Router.HandleFunc("/api/{tahun_awal}/{tahun_akhir}", middleware.Jsonheader(s.GetAll)).Methods("GET")
	

but when i asking for println vars, is empty

func (server *Server) GetAll(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	fmt.Println("Nilai tahunAwal:", vars["tahunAwal"])
	fmt.Println("Nilai tahunAkhir:", vars["tahunAkhir"])

im using reference to use 1 struct that have many func