[Go]当把json解析到interface{}时 , 对应的真正类型

func send(w http.ResponseWriter, r *http.Request){
    w.Header().Set("content-type", "text/json;charset=utf-8;")
    var sendData map[string]interface{}
    bodyBytes,err:=ioutil.ReadAll(r.Body)
    if err!=nil{
        msg, _ := json.Marshal(tools.JsonResult{Code: 400, Msg: "操作失败,"+err.Error()})
        w.Write(msg)
        return
    }

    err = json.Unmarshal(bodyBytes, &sendData)
    if err!=nil{
        msg, _ := json.Marshal(tools.JsonResult{Code: 400, Msg: "操作失败,"+err.Error()})
        w.Write(msg)
        return
    }

    smtpServer:=sendData["smtp"].(string)
    smtpFrom:=sendData["from"].(string)
    msg, _ := json.Marshal(tools.JsonResult{Code: 200, Msg: smtpServer+smtpFrom})
    w.Write(msg)
}