我无法验证传递给POST端点的JSON正文是否与为可接受的JSON正文创建的结构匹配。任何帮助将不胜感激

type NewUser struct {
    UserID   string `json:"user_id"`
    username string `json:"user_name"`
}

func AddUser(w http.ResponseWriter,r *http.Request) {
    w.Header().Set("Content-Type","application/json")

    decoder := json.NewDecoder(r.Body)

    var user NewUser
    err := decoder.Decode(&user)

    if err != nil {
        http.Error(w,err.Error(),http.StatusBadRequest)
    }
    user.UserID != NewUser.UserID{
        http.Error(w,"error",http.StatusBadRequest),}

}