code: func (oauth *Oauth) CheckAccessToken(accessToken, openID string) (b bool, err error) {
  	urlStr := fmt.Sprintf(checkAccessTokenURL, accessToken, openID)
  	var response []byte
  	response, err = util.HTTPGet(urlStr)
  	if err != nil {
  		return
  	}
  	var result util.CommonError
  	err = json.Unmarshal(response, &result)
  	if err != nil {
  		return
  	}
  	if result.ErrCode != 0 {
  		b = false
  		return
  	}
  	b = true
  	return
  }
docs: //CheckAccessToken 检验access_token是否有效