gin入参多次获取

在middleware层不要用ShouldBind函数绑定body中的参数，因为ShouldBind执行完后，request中body就空了，业务层就拿不到body了。用下面的代码即可，先拿后放。

userIdReq := new(UserIdReq)
var err error
if c.Request.Method == "GET" {
    err = c.ShouldBindQuery(userIdReq)
} else if (c.Request.Method == "POST" || c.Request.Method == "DELETE") && strings.Contains(c.ContentType(), "application/json") {
    body, _ := c.GetRawData()
    c.Request.Body = io.NopCloser(bytes.NewBuffer(body))
    err = json.Unmarshal(body, userIdReq)
} else {
    c.Abort() 
    return
}