var DefaultTransport = func() RoundTripper {
	switch {
	case js.Global.Get("fetch") != js.Undefined && js.Global.Get("ReadableStream") != js.Undefined:
		return &fetchTransport{}
	case js.Global.Get("XMLHttpRequest") != js.Undefined:
		return &XHRTransport{}
	default:
		return noTransport{}
	}
}()