code: func (s *Services) WithTag(tag string) ([]Service, error) {
  	result := []Service{}
  	for _, services := range *s {
  		for i := range services {
  			service := services[i]
  			for _, t := range service.Tags {
  				if strings.EqualFold(tag, t) {
  					result = append(result, service)
  					break
  				}
  			}
  		}
  	}
  
  	if len(result) > 0 {
  		return result, nil
  	}
  
  	return nil, fmt.Errorf("no services with tag %s", tag)
  }
docs: // WithTag finds services with the specified tag.