simpleXmlLambdaResponse.js

var parseString = require('xml2js').parseString;

exports.handler = function (event, context, callback) {
  
  parseString(event.body, function (err, result) {
    event.body = result;
    let respondToGateway = {
      statusCode: '200',
      body      : JSON.stringify({
        event: event,
        context: context
      }),
      headers   : {
        'Content-Type': 'application/json'
      }
    };
    callback(null, respondToGateway);
  });
};