code: func Ensure(table Table, tx *sql.Tx) (bool, error) {
  	var inserted bool
  	err := table.Select(tx)
  	if err == sql.ErrNoRows {
  		err = table.Insert(tx)
  		inserted = true
  	}
  	return inserted, err
  }
docs: // Ensure ensures the value is present in the database. It calls
  // Select, and if no rows are returned, it calls Insert. The boolean
  // will be true if the value was inserted. This value is meaningless
  // if err is non-nil.