I have a function :

```
    func (db *DBSqlx) GetRefreshToken(oldToken string, tx *sqlx.Tx) (string, error) {
    var refreshToken string

    err := db.TemplateGet(
        tx,
        &refreshToken,
        `query`,
        oldToken,
    )

    if err != nil {
        return "", errors.Wrap(err, "не удалось запросить рефреш токен для указанного токена")
    }

    return refreshToken, err
}

```

How to write a test for this function with mock response?

DB has type :

```
    type DBSqlx struct {
    PgConn    *sqlx.DB
    PgConnCtx context.Context
}

```

I tried to write this code. But I don't understand how to use the package correctly.

```
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()

mock.ExpectQuery("query").WillReturnRows()

```