Update session.go

move expire in line 154 to 247, because it will cause session_cookie not writen to explorer

@@ -151,7 +151,6 @@ func (manager *Manager) SessionStart(w http.ResponseWriter, r *http.Request) (se
 			Domain:   manager.config.Domain}
 		if manager.config.CookieLifeTime >= 0 {
 			cookie.MaxAge = manager.config.CookieLifeTime
-			cookie.Expires = time.Now().Add(time.Duration(manager.config.CookieLifeTime) * time.Second)
 		}
 		if manager.config.EnableSetCookie {
 			http.SetCookie(w, cookie)
@@ -245,6 +244,7 @@ func (manager *Manager) SessionRegenerateId(w http.ResponseWriter, r *http.Reque
 	}
 	if manager.config.CookieLifeTime >= 0 {
 		cookie.MaxAge = manager.config.CookieLifeTime
+		cookie.Expires = time.Now().Add(time.Duration(manager.config.CookieLifeTime) * time.Second)
 	}
 	http.SetCookie(w, cookie)
 	r.AddCookie(cookie)