Tell about transaction isolation levels.

Transaction isolation levels determine how and when the changes made by one transaction become visible to other transactions, as well as what anomalies may occur during concurrent data access. The main isolation levels:

• Read Uncommitted — the lowest level of isolation. A transaction can see uncommitted changes made by others (dirty read). Anomalies are possible.

• Read Committed — a transaction only sees data committed by others. It prevents dirty reads but allows non-repeatable reads.

• Repeatable Read — guarantees that data read at the beginning of a transaction will not change until it ends. It prevents non-repeatable reads but allows phantom reads.

• Serializable — the strictest level. Transactions execute as if they were sequential, preventing all types of anomalies, including phantom reads. It provides maximum integrity but reduces concurrency.

In Go, isolation levels depend on the database and driver used but conceptually work the same. For example, when working with PostgreSQL via database/sql, you can set the isolation level through SQL commands or transaction parameters.