func ModuleHostname(c context.Context, module, version, instance string) (string, error) {
	req := &modpb.GetHostnameRequest{}
	if module != "" {
		req.Module = &module
	}
	if version != "" {
		req.Version = &version
	}
	if instance != "" {
		req.Instance = &instance
	}
	res := &modpb.GetHostnameResponse{}
	if err := internal.Call(c, "modules", "GetHostname", req, res); err != nil {
		return "", err
	}
	return *res.Hostname, nil
}
func ModuleHostname(c context.Context, module, version, instance string) (string, error) {
	req := &modpb.GetHostnameRequest{}
	if module != "" {
		req.Module = &module
	}
	if version != "" {
		req.Version = &version
	}
	if instance != "" {
		req.Instance = &instance
	}
	res := &modpb.GetHostnameResponse{}
	if err := internal.Call(c, "modules", "GetHostname", req, res); err != nil {
		return "", err
	}
	return *res.Hostname, nil
}
// ModuleHostname returns a hostname of a module instance.
// If module is the empty string, it refers to the module of the current instance.
// If version is empty, it refers to the version of the current instance if valid,
// or the default version of the module of the current instance.
// If instance is empty, ModuleHostname returns the load-balancing hostname.