chore: use http.Status* instead of hard code (#1482)

render/redirect.go

@@ -16,6 +16,8 @@ type Redirect struct {
 }
 
 func (r Redirect) Render(w http.ResponseWriter) error {
+	// todo(thinkerou): go1.6 not support StatusPermanentRedirect(308)
+	// when we upgrade go version we can use http.StatusPermanentRedirect
 	if (r.Code < 300 || r.Code > 308) && r.Code != 201 {
 		panic(fmt.Sprintf("Cannot redirect with status code %d", r.Code))
 	}