code: func (db *DB) Beginx() (*Tx, error) {
  	tx, err := db.DB.Begin()
  	if err != nil {
  		return nil, err
  	}
  	return &Tx{Tx: tx, driverName: db.driverName, unsafe: db.unsafe, Mapper: db.Mapper}, err
  }
docs: // Beginx begins a transaction and returns an *sqlx.Tx instead of an *sql.Tx.