address.go

func getExistingAddressId(tx *sql.Tx, address string) (int64, error) {
  var result sql.NullInt64
  if err := tx.QueryRow("SELECT id FROM wallet WHERE `address`=?", address).
    Scan(&result); err != nil && err != sql.ErrNoRows {
    return 0, err
  }

  return result.Int64, nil
}

func insertNewAddress(tx *sql.Tx, address string) (int64, error) {
  res, err := tx.Exec("INSERT INTO wallet (address) VALUES (?)", address)
  if err != nil {
    return 0, err
  }

  return res.LastInsertId()
}

func getAddressId(db *sql.DB, address string) (id int64, err error) {
  tx, err := db.Begin()
  if err != nil {
    return 0, err
  }

  defer func() {
    if err != nil {
      tx.Rollback()
    } else {
      tx.Commit()
    }
  }()

  if id, err = getExistingAddressId(tx, address); err != nil || id != 0 {
    return
  }

  return insertNewAddress(tx, address)
}