go get github.com/go-macaron/authz

package main
import (
	"net/http"
	"github.com/casbin/casbin"
	"github.com/go-macaron/authz"
	"gopkg.in/macaron.v1"
)
func main() {
	m := macaron.New()
	// load the casbin model and policy from files, database is also supported.
	e := casbin.NewEnforcer("authz_model.conf", "authz_policy.csv")
	m.Use(authz.Authorizer(e))
	// define your handler, this is just an example to return HTTP 200 for any requests.
	// the access that is denied by authz will return HTTP 403 error.
	m.Use(func(res http.ResponseWriter, req *http.Request) {
    	res.Write([]byte("Access allowed. "))
    })
}