microservice with node and needle

Question

I'm trying to make my monolithic application written in node and express to a microservice application in node, needle(to communicate between microservices) and express. My architecture is as follows,

• I have a microservice called gateway_service to handle all the requests from frontend UI
• I have another microservice called users_service to handle requests related to users, users_service uses passport local strategy to manage sessions and this session id is sent as a cookie by passport

When I try to change my application to microservice I'm doing the following

• Whenever I receive a request from my client say, postman in gateway_service I can see the cookie coming through header, and I'm able to pass it to user_service by setting headers option as mentioned in needle.
• How to send the cookie that I receive from user_service to the postman back to he can save the cookie(in case of first hit)??

I'm adding a small code snippet, hoping it will help? Am I doing it in the right way?? when I'm doing as shown below Im getting the error "Cannot set headers after they are sent to the client"

function (req, res, next) {
  var options = {
    headers: req.headers,
    parse_cookies:true
  }
    needle.post(url + "login", req.body, options, function (error, response, body) {
      if (!error) {
        res.writeHead(response.statusCode,response.headers);
        res.send(body)
        console.log(res);
        next();


      } else {
        console.log("error in  info from users micro service");
        res.send(error);
        next();
      }
    });
  },