func demoVC() -> DemoVC {
        let navVC = tabBarVC.viewControllers?[2] as! UINavigationController
        return navVC.viewControllers.first as! DemoVC
    }

func logout() {
        if let tabBarVC = tabBarVC {
            let vc = tabBarVC.storyboard?.instantiateViewController(withIdentifier: "WelcomeVC")
            UIApplication.shared.keyWindow?.rootViewController = vc
            //socket close
            SocketManager.sharedInstance.logoutFromWebSocket()

            //remove purshases
            KeychainManager.sharedInstance.removeAll()
        }
    }