code: private void writeHeaders(final YokeRequest request, final FileProps props) {
  
          MultiMap headers = request.response().headers();
  
          if (!headers.contains("etag")) {
              headers.set("etag", "\"" + props.size() + "-" + props.lastModifiedTime() + "\"");
          }
  
          if (!headers.contains("date")) {
              headers.set("date", format(new Date()));
          }
  
          if (!headers.contains("cache-control")) {
              headers.set("cache-control", "public, max-age=" + maxAge / 1000);
          }
  
          if (!headers.contains("last-modified")) {
              headers.set("last-modified", format(new Date(props.lastModifiedTime())));
          }
      }
docs: Create all required header so content can be cache by Caching servers or Browsers
  
  @param request
  @param props