Who makes the decision to rollback?

The decision to rollback a transaction in Go (Golang) is usually made by the code managing the transaction, most often the developer writing the business logic. In the standard library database/sql, the rollback is explicitly called with the method tx.Rollback() if an error occurs or if the logic requires undoing changes.

Example:

trx, err := db.Begin()
if err != nil {
    // handle error
}

// Perform operations
if err := doSomething(trx); err != nil {
    trx.Rollback() // rollback on error
    return err
}

err = trx.Commit() // confirm changes

Thus, the decision to rollback is made by the developer based on the results of the operations and business logic, not automatically by the system.