passport.use(new WechatStrategy({
        appID: {APPID},
        name:{默认为wechat,可以设置组件的名字}
        appSecret: {APPSECRET},
        client:{wechat|web},
        callbackURL: {CALLBACKURL},
        scope: {snsapi_userinfo|snsapi_base},
        state:{STATE},
        getToken: {getToken},
        saveToken: {saveToken}
      },
      function(accessToken, refreshToken, profile,expires_in, done) {
        return done(err,profile);
      }
));

The `callbackURL`, `scope` and `state` can be overwritten in `passport.authenticate` middleware.

The `getToken` and `saveToken` can be provided to initialize Wechat OAuth instance.

  router.get('/auth/wechat', passport.authenticate('wechat', options));

  router.get('/auth/wechat/callback', passport.authenticate('wechat', {
    failureRedirect: '/auth/fail',
    successReturnToOrRedirect: '/'
  }));