golang fiber中写一个微信支付函数库

以下是一个使用Golang Fiber框架编写的微信支付函数库的示例代码：

package wechatpay

import (
    "bytes"
    "crypto/tls"
    "encoding/xml"
    "fmt"
    "io/ioutil"
    "net/http"
    "sort"
    "strings"
    "time"
)

type WechatPay struct {
    AppID     string // 微信公众号或开放平台APP的唯一标识
    MchID     string // 商户号
    Key       string // 商户支付密钥
    NotifyURL string // 支付结果通知地址
}

type UnifiedOrderRequest struct {
    XMLName        xml.Name `xml:"xml"`
    AppID          string   `xml:"appid"`
    MchID          string   `xml:"mch_id"`
    NonceStr       string   `xml:"nonce_str"`
    Body           string   `xml:"body"`
    OutTradeNo     string   `xml:"out_trade_no"`
    TotalFee       int      `xml:"total_fee"`
    SpbillCreateIP string   `xml:"spbill_create_ip"`
    NotifyURL      string   `xml:"notify_url"`
    TradeType      string   `xml:"trade_type"`
    OpenID         string   `xml:"openid"`
    Sign           string   `xml:"sign"`
}

type UnifiedOrderResponse struct {
    XMLName     xml.Name `xml:"xml"`
    ReturnCode  string   `xml:"return_code"`
    ReturnMsg   string   `xml:"return_msg"`
    AppID       string   `xml:"appid"`
    MchID       string   `xml:"mch_id"`
    NonceStr    string   `xml:"nonce_str"`
    Sign        string   `xml:"sign"`
    ResultCode  string   `xml:"result_code"`
    PrepayID    string   `xml:"prepay_id"`
    TradeType   string   `xml:"trade_type"`
}

func (wp *WechatPay) UnifiedOrder(body, outTradeNo, spbillCreateIP, tradeType, openID string, totalFee int) (*UnifiedOrderResponse, error) {
    nonceStr := fmt.Sprintf("%d", time.Now().UnixNano())
    req := &UnifiedOrderRequest{
        AppID:          wp.AppID,
        MchID:          wp.MchID,
        NonceStr:       nonceStr,
        Body:           body,
        OutTradeNo:     outTradeNo,
        TotalFee:       totalFee,
        SpbillCreateIP: spbillCreateIP,
        NotifyURL:      wp.NotifyURL,
        TradeType:      tradeType,
        OpenID:         openID,
    }
    req.Sign = wp.sign(req)

    buf := bytes.NewBuffer(nil)
    xml.NewEncoder(buf).Encode(req)

    client := &http.Client{
        Transport: &http.Transport{
            TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
        },
    }
    resp, err := client.Post("https://api.mch.weixin.qq.com/pay/unifiedorder", "application/xml;charset=utf-8", buf)
    if err != nil {
        return nil, err
    }
    defer resp.Body.Close()

    respBody, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        return nil, err
    }

    var unifiedOrderResp UnifiedOrderResponse
    err = xml.Unmarshal(respBody, &unifiedOrderResp)
    if err != nil {
        return nil, err
    }

    return &unifiedOrderResp, nil
}

func (wp *WechatPay) sign(req *UnifiedOrderRequest) string {
    m := make(map[string]string)
    m["appid"] = req.AppID
    m["mch_id"] = req.MchID
    m["nonce_str"] = req.NonceStr
    m["body"] = req.Body
    m["out_trade_no"] = req.OutTradeNo
    m["total_fee"] = fmt.Sprintf("%d", req.TotalFee)
    m["spbill_create_ip"] = req.SpbillCreateIP
    m["notify_url"] = req.NotifyURL
    m["trade_type"] = req.TradeType
    m["openid"] = req.OpenID

    var keys []string
    for k := range m {
        keys = append(keys, k)
    }
    sort.Strings(keys)

    var buf bytes.Buffer
    for _, k := range keys {
        v := m[k]
        if v != "" {
            buf.WriteString(k)
            buf.WriteString("=")
            buf.WriteString(v)
            buf.WriteString("&")
        }
    }
    buf.WriteString("key=")
    buf.WriteString(wp.Key)

    return strings.ToUpper(fmt.Sprintf("%x", md5.Sum(buf.Bytes())))
}