我正在嘗試使用 sqlmock 對我的 go 代碼進行單元測試。這是我要測試的原始代碼。func enrollCourse(db *gorm.DB, user_id string ,course_id string) error {    user := &usermodels.User{}    ref := db.First(user, "uuid = ?", user_id)    userPb := user.Protobuf()    fmt.Printf("user name %+v", user.name)    ....}這是我的單元測試func TestEnrollCourse(t *testing.T){    db, mock, err := sqlmock.New()    if err != nil {        t.Fatalf("an error '%s' was not expected when opening a stub database connection", err)    }    defer db.Close()    rows := sqlmock.NewRows([]string{"user_id","user_name"}).        AddRow(1, "John")    mock.ExpectQuery(regexp.QuoteMeta(`SELECT * FROM "users" WHERE uuid = $1`)).WithArgs("user-fd3746c8-d32f-4fb8-8f6a-b6d72dcf2969").WillReturnRows(rows)        gdb, err := gorm.Open(postgres.New(postgres.Config{                       Conn: db,               }), &gorm.Config{})    enrollCourse(gdb, "user-fd3746c8-d32f-4fb8-8f6a-b6d72dcf2969", "english_course")    ....}我期待 fmt.Printf("user name %+v", user.name) 打印用戶名，但它為零。如何正確地將 protobuf 對象傳遞給 addRow？