InitRequestDBContext initialize db context for the request.

NewContextWithContext creates a new context.DB from context.

NewTxContextWithContext creates a new context.Tx from context.

ReadOnly runs do in a transaction and rolls back always.

WithTx commits if do finishes without error and rolls back otherwise.

MockTxContext implements and record db.TxContext methods FIXME: It assumes that the TxContext does not get reuse.

Context provides db with the interface for retrieving an interface to execute sql.

Scanner is sqlx.Row or sqlx.Rows.

TxContext provides the interface for managing transaction.