code: func (au *LocalAuthenticator) Authenticate(user, password string) bool {
  	if au == nil {
  		return true
  	}
  
  	au.mux.RLock()
  	defer au.mux.RUnlock()
  
  	if len(au.kvs) == 0 {
  		return true
  	}
  
  	v, ok := au.kvs[user]
  	return ok && (v == "" || password == v)
  }
docs: // Authenticate checks the validity of the provided user-password pair.