code: func newStaticAuthenticator(users []string) (*staticAuthenticator, error) {
  	sa := &staticAuthenticator{
  		credentials: make(map[string]string),
  	}
  	for _, u := range users {
  		fields := strings.Split(u, ":")
  		if len(fields) != 2 {
  			return nil, fmt.Errorf("invalid format of basic auth entry '%v' expected 'user:pass'", u)
  		}
  		sa.credentials[fields[0]] = fields[1]
  	}
  	return sa, nil
  }
docs: // newStaticAuthenticator creates new instance of static authenticator.
  // Argument `users` is a slice of colon-separated username and password couples.