code: function endpoint(func, opts) {
    const options = opts || {};
  
    /**
      runs endpoint handler, use res.send(statusCode, body) finish api call successfully
      @name endpointHandler
      @function
      @param {req} req
      @param {res} res
  
    */
    return function endpointHandler() {
      // call mapper with endpointHandlers args
      const input = eventMapper.apply({ options }, arguments);
      const req = input.req;
      const res = input.res;
  
      return func(req, res);
    };
  }
docs: This is a handler function that is invoked by cloud trigger.
  AWS Example function handler
  [Lambda Function Handler (Node.js) Docs](http://docs.aws.amazon.com/lambda/latest/dg/nodejs-prog-model-handler.html)
  @name CloudFunctionHandler
  @function
   
  HOC function that maps the ApiGateway CloudEndpoint, Azure HttpTrigger  event api to
  Req and Res similar to that of Express
  @function
  @param {CloudFunctionHandler} func - Google, AWS, Azure Function Handler
  @param {Object} opts - Configuration object for an function endpoint
  @param {Object} opts.headers - Default headers object.
  Default headers are set before handler is called.
  @param {string} opts.headers.* - Header key value pair.
  Example - `Content-Type: 'application/json'`
  
  @returns {endpointHandler} endpointHandler - Converts event,
  context to req, res api for Lambda Function Handler