private void listLinksRoutine(RoutingContext routingContext) {
   routingContext.response().setChunked(true);
   FileSystem fs = routingContext.vertx().fileSystem();
   StringBuilder allLinks = linksIntoThePage(fs);
   routingContext.response().write(allLinks.toString());
   routingContext.response().end();
 }
  @Override
  public void render(
      RoutingContext context, String templateFileName, Handler<AsyncResult<Buffer>> handler) {
    try {
      Template template = cache.get(templateFileName);
      if (template == null) {
        // real compile
        synchronized (this) {
          loader.setVertx(context.vertx());
          // Compile
          template = config.getTemplate(adjustLocation(templateFileName));
        }
        cache.put(templateFileName, template);
      }

      Map<String, RoutingContext> variables = new HashMap<>(1);
      variables.put("context", context);

      try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
        template.process(variables, new OutputStreamWriter(baos));
        handler.handle(Future.succeededFuture(Buffer.buffer(baos.toByteArray())));
      }

    } catch (Exception ex) {
      handler.handle(Future.failedFuture(ex));
    }
  }