buffer 循环读取

func getPayChanel(no string) (string, error) {
	url := "https://ccdcapi.alipay.com/validateAndCacheCardInfo.json?_input_charset=utf-8&cardNo=" + no + "&cardBinCheck=true"

	// 超时时间：5秒
	client := &http.Client{Timeout: 5 * time.Second}
	resp, err := client.Get(url)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()
	var buffer [512]byte
	result := bytes.NewBuffer(nil)
	for {
		n, err := resp.Body.Read(buffer[0:])
		result.Write(buffer[0:n])
		if err != nil && err == io.EOF {
			break
		} else if err != nil {
			return "", err
		}
	}

	paramsBody := map[string]interface{}{}
	if err := json.Unmarshal(result.Bytes(), &paramsBody); err != nil {
		return "", err
	}
	typeStr, ok := paramsBody["bank"]
	if !ok {
		return "", e.New("map error")
	}
	str, ok := typeStr.(string)
	if !ok {
		return "", e.New("map error")
	}

	return str, nil
}