code: func (wfe *WebFrontEndImpl) Options(response http.ResponseWriter, request *http.Request, methodsStr string, methodsMap map[string]bool) {
  	// Every OPTIONS request gets an Allow header with a list of supported methods.
  	response.Header().Set("Allow", methodsStr)
  
  	// CORS preflight requests get additional headers. See
  	// http://www.w3.org/TR/cors/#resource-preflight-requests
  	reqMethod := request.Header.Get("Access-Control-Request-Method")
  	if reqMethod == "" {
  		reqMethod = "GET"
  	}
  	if methodsMap[reqMethod] {
  		wfe.setCORSHeaders(response, request, methodsStr)
  	}
  }
docs: // Options responds to an HTTP OPTIONS request.