axios serverless with third-party API

axiosServerless.js

const axios = require("axios");

const mailChimp = {
  preLaunchListId: "ff8c031f0e",  // you can find yours in your mailchimp dashboard
  apiUrl: "https://us2.api.mailchimp.com/3.0/" // this too
};

module.exports.addToBetaUserList = function(event, context, callback) {
  const body = JSON.parse(event.body); // accessing the POST body payload. yours might have different structure and names
  const auth = {
    username: "johnDough",
    password: process.env.MAILCHIMP_API_KEY  // we set this earlier in the serverless.yml file
  };
  const user = {
    email_address: body.emailAddress,  // we set 'emailAddress' key in the front-end
    status: "subscribed" //  signifies user is subscribed for mailchimp(https://goo.gl/ejX1nu) 
  };

  axios
    .post(
      `${mailChimp.apiUrl}lists/${mailChimp.preLaunchListId}/members/`,
      user,
      { auth, headers: { "content-type": "application/json" } }
    )
    .then(function() {
      const response = {
        statusCode: 200,
        headers: {
          "Access-Control-Allow-Origin": "*", // Required for CORS support to work
          "Access-Control-Allow-Credentials": true // Required for cookies, authorization headers with HTTPS
        },
        body: JSON.stringify({
          message: "Successfully added to beta user list!"
        })
      };
      callback(null, response);
    })
    .catch(e => {
      const error = e.response.data;
      const errorResponse = {
        statusCode: error.status,
        headers: {
          "Access-Control-Allow-Origin": "*", // Required for CORS support to work
          "Access-Control-Allow-Credentials": true // Required for cookies, authorization headers with HTTPS
        },
        body: JSON.stringify({
          message: error.title
        })
      };
      callback(null, errorResponse);
    });
};