使用http.PostForm请求报错x509 certificate signed by unknown authority，使用如下代码解决（START-END注释部分，并且http.PostForm改为client.PostForm）：

func (kd *kd100) Query(num, comCode string) (map[string]interface{}, error) {
    paramData := make(map[string]string)
    paramData["com"] = comCode //快递公司编码
    paramData["num"] = num     //快递单号

    str, _ := json.Marshal(paramData)
    paramJson := string(str)
    sign := kd.getSign(paramJson)

    // 解决 Go https请求报错x509 certificate signed by unknown authority 问题 START
    tr := &http.Transport{
        TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
    }

    client := &http.Client{
        Timeout:   15 * time.Second,
        Transport: tr,
    }
    //END

    postRes, postErr := client.PostForm(postUrl, url.Values{"customer": {kd.customer}, "sign": {sign}, "param": {paramJson}})
    if postErr != nil {
        _ = logx.Error(postErr)
        return nil, errors.New(postErr.Error())
    }
    postBody, err := ioutil.ReadAll(postRes.Body)
    if err != nil {
        _ = logx.Error(postErr)
        return nil, errors.New("查询失败,请至快递公司官网自行查询")
    }

    fmt.Println(string(postBody))

    resp := make(map[string]interface{})
    err = json.Unmarshal(postBody, &resp)
    if err != nil {
        _ = logx.Error(postErr)
        return nil, errors.New("查询失败,请至快递公司官网自行查询")
    }

    return resp, nil
}