switch err.HTTPStatusCode {
	case http.StatusServiceUnavailable, http.StatusTooManyRequests:
		// Set retry-after header to indicate user-agents to retry request after 60 seconds.
		// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Retry-After
		w.Header().Set(xhttp.RetryAfter, "60")
	}

	switch err.Code {
	case "InvalidRegion":