HELP...Refresh the page after login, session disappears
Page running 127.0.0.1:3000
Server running 127.0.0.1:8888

page request code:
```js
await axios.get(`${host}${path}`, { params: params, withCredentials: true });
```

Refresh the page after login, session disappears.
![image](https://user-images.githubusercontent.com/26628346/65307224-e772bd80-dbb9-11e9-8c66-f44bc639900d.png)
![image](https://user-images.githubusercontent.com/26628346/65307360-2c96ef80-dbba-11e9-86ed-b184fec757e5.png)

```js
router.post('/', async ctx => {
  const { db } = ctx;
  try {
    const { username, password } = ctx.request.fields;
    const userList = await db.query('SELECT * FROM user WHERE username = ? AND password = ?', [username, password]);
    if (userList.length > 0) {
      ctx.session['userId'] = userList[0].id;
      console.log('ctx.session: ', ctx.session);
      ctx.body = { code: 0 }
    } else {
      ctx.body = { code: -1, msg: '登录失败，用户不存在或密码错误！' };
    }
  } catch (e) {
    console.log(e);
  }
});
```

```js
// 处理跨域
server.use(cors({
  credentials: true, //带cookies
}));

// session处理
server.keys = ['asdasdasdasgfsdg'];
server.use(session({
  maxAge: 3 * 24 * 60 * 60 * 1000,
  rolling: true,
  renew: true
}, server));
const sessionDeal = require('./lib/check-user.js');
server.use(async (ctx, next) => sessionDeal(ctx, server, next));

/**
 * /lib/check-user.js [sessionDeal]
 * 通用校验是否登录成功的合法用户
 */
module.exports = async (ctx, server, next) => {
  if (!ctx.path.includes('/user/login')) {
    console.log('ctx.cookie: ', ctx.cookies);
    console.log('ctx.session: ', ctx.session);
    const { userId } = ctx.session;
    if (userId && Number(userId) > 0) {
      server.context.userId = userId;
      await next();
    } else {
      // 401 无权访问需登录
      ctx.throw(401, {
        code: 1,
        msg: '请先登录'
      });
    }
  } else {
    await next();
  }
};

```