func doAction(
	c *fiber.Ctx,
	addr string,
	action func(cli *fasthttp.Client, req *fasthttp.Request, resp *fasthttp.Response) error,
	clients ...*fasthttp.Client,
) error {
	var cli *fasthttp.Client

	// set local or global client
	if len(clients) != 0 {
		cli = clients[0]
	} else {
		lock.RLock()
		cli = client
		lock.RUnlock()
	}

	req := c.Request()
	res := c.Response()
	originalURL := utils.CopyString(c.OriginalURL())
	defer req.SetRequestURI(originalURL)

	copiedURL := utils.CopyString(addr)
	req.SetRequestURI(copiedURL)
	// NOTE: if req.isTLS is true, SetRequestURI keeps the scheme as https.
	// Reference: https://github.com/gofiber/fiber/issues/1762
	if scheme := getScheme(utils.UnsafeBytes(copiedURL)); len(scheme) > 0 {
		req.URI().SetSchemeBytes(scheme)
	}

	req.Header.Del(fiber.HeaderConnection)
	if err := action(cli, req, res); err != nil {
		return err
	}
	res.Header.Del(fiber.HeaderConnection)
	return nil
}