return "", err

    }

    nonceStr := GetRandomString(32)

    //请求UnifiedOrder的代码

    var yourReq UnifyOrderReq

    yourReq.Appid = WX_APP_ID //微信开放平台我们创建出来的app的app id

    yourReq.Body = bookOrder.LineNum

    yourReq.Mch_id = WX_MCH_ID

    yourReq.Nonce_str = nonceStr

    yourReq.Notify_url = WX_NOTIFY_URL

    yourReq.Trade_type = "APP"

    yourReq.Spbill_create_ip = WX_INVOKE_API_IP

    yourReq.Total_fee = int(bookOrder.TotalPrice * 100) //单位是分

    yourReq.Out_trade_no = orderNo

    var m map[string]interface{}

    m = make(map[string]interface{}, 0)

    m["appid"] = yourReq.Appid

    m["body"] = yourReq.Body

    m["mch_id"] = yourReq.Mch_id

    m["notify_url"] = yourReq.Notify_url

    m["trade_type"] = yourReq.Trade_type

    m["spbill_create_ip"] = yourReq.Spbill_create_ip

    m["total_fee"] = yourReq.Total_fee

    m["out_trade_no"] = yourReq.Out_trade_no

    m["nonce_str"] = yourReq.Nonce_str

    yourReq.Sign = o.wxpayCalcSign(m, WX_PAY_KEY) // 这个是计算wxpay签名的函数上面已贴出

    bytes_req, err := xml.Marshal(yourReq)

    if err != nil {

        log4go.Error("wxUnifyChargeReq(): xml.Marshal error:%s", err)

        return "", err

    }

    str_req := string(bytes_req)

    //wxpay的unifiedorder接口需要http body中xmldoc的根节点是<xml></xml>这种，所以这里需要replace一下

    str_req = strings.Replace(str_req, "XUnifyOrderReq", "xml", -1)

    bytes_req = []byte(str_req)

    log4go.Debug("wxUnifyChargeReq()...str_req:%s", str_req)

    //发送unified order请求.

    req, err := http.NewRequest("POST", WX_UNIFIEDORDER_API, bytes.NewReader(bytes_req))

    if err != nil {

        log4go.Error("wxUnifyChargeReq(): http.NewRequest error:%s", err)

        return "", err

    }

    req.Header.Set("Accept", "application/xml")

    //这里的http header的设置是必须设置的.

    req.Header.Set("Content-Type", "application/xml;charset=utf-8")