code: func requestNew(options options) rest.Request {
  	if options.Host == "" {
  		options.Host = "https://api.sendgrid.com"
  	}
  
  	requestHeaders := map[string]string{
  		"Authorization": "Bearer " + options.Key,
  		"User-Agent":    "sendgrid/" + Version + ";go",
  		"Accept":        "application/json",
  	}
  
  	if len(options.Subuser) != 0 {
  		requestHeaders["On-Behalf-Of"] = options.Subuser
  	}
  
  	return rest.Request{
  		BaseURL: options.baseURL(),
  		Headers: requestHeaders,
  	}
  }
docs: // requestNew create Request
  // @return [Request] a default request object