code: func getRole(c redis.Conn) (string, error) {
  	res, err := c.Do("ROLE")
  	if err != nil {
  		return "", err
  	}
  	rres, ok := res.([]interface{})
  	if ok {
  		return redis.String(rres[0], nil)
  	}
  	return "", errors.New("redigo: can not transform ROLE reply to string")
  }
docs: // getRole is a convenience function supplied to query an instance (master or
  // slave) for its role. It attempts to use the ROLE command introduced in
  // redis 2.8.12.