code: func (s *Store) ServiceNames() []string {
  	s.mu.RLock()
  	defer s.mu.RUnlock()
  
  	var a []string
  	for name := range s.data.Services {
  		a = append(a, name)
  	}
  	sort.Strings(a)
  
  	return a
  }
docs: // ServiceNames returns a sorted list of existing service names.