aws-lambda-fn.js

var params = {
  "method": "GET",
  "hostname": "www.<URL>.com",
  "port": null,
  "headers": {
    "cache-control": "no-cache"
  }
};

var secret = process.env.SECRETENV;

exports.handler = (event, context, callback) => {
  
  var qs = event['queryStringParameters'] //Gets parameters sent through the API Endpoint
  
  qs = Object.keys( qs ).map( key => `${key}=${qs[key]}` ).join('&') //Adds parameters as a query string to URL

  params['headers']['secret'] = secret //Adds secret as header parameter
  params['path'] = '/url-path?' + qs //Adds query string to URL
  
  var req = http.request(params, function (res) {
    var chunks = [];

    res.on("data", function (chunk) {
      chunks.push(chunk);
    });

    res.on("end", function () {
      var body = Buffer.concat(chunks);
      parseString(body.toString(), function (err, result) {
        
        //This is an AWS Lambda convention to end a function
        context.succeed( {
            "statusCode": 200,
            "headers": {
              'Access-Control-Allow-Origin': '*'
            },
            "body": JSON.stringify(result)
        } ); //Ends Lambda function by returning API response
      });
    });
  });

  req.end();
}