function Payment(callback){
    request({
        method: 'POST',
        url: 'https://secure.snd.payu.com/pl/standard/user/oauth/authorize', //server B
        headers: {
            'Content-Type': 'application/x-www-form-urlencoded',
        },
        body: "credentials_id"
    },  function (error, response, body) {
            callback(null, JSON.parse(body).access_token);
      }
    )
}

router.post('/sendOrders', function(req, res){
  Payment(function(err, body){
     request({
       method: 'POST',
       url: 'https://secure.snd.payu.com/api/v2_1/orders/',
       headers: {
          'Content-Type': 'application/json',
           'Authorization': 'Bearer ' + body
        },
        body: JSON.stringify({
           "notifyUrl": "http://test:8080/notify", //server A
           "continueUrl": "http://test:8080/continue", //server A
           "customerIp": "xxxxx",
           "settings":{
              "invoiceDisabled":"true"
        },
           "products": product
      })
    }, function(error, response, body){
          res.send({ success: true, body: JSON.parse(body)})
  }) ;
})

router.get('/notify', function(req, res){
    request({
        method: 'GET',
        url: 'http://test/notify', //server A
        headers: {
            'Content-Type': 'application/json',
        },
    }, function(error, response, body){
        console.log(body)
    })
})