use case level transaction interface

txDataservice.go

// TxDataInterface represents operations needed for transaction support.
// It only needs to be implemented once for each database
// For sqlGdbc, it is implemented for SqlDBTx in transaction.go
type TxDataInterface interface {
	// TxBegin starts a transaction. It gets a DB handler from the receiver and return a TxDataInterface, which has a
	// *sql.Tx inside. Any data access wrapped inside a transaction will go through the *sql.Tx
	TxBegin() (TxDataInterface, error)
	// TxEnd is called at the end of a transaction and based on whether there is an error, it commits or rollback the
	// transaction.
	// txFunc is the business function wrapped in a transaction
	TxEnd(txFunc func() error) error
	// Return the underline transaction handler, sql.Tx
	GetTx() gdbc.SqlGdbc
}

// This interface needs to be included in every data service interface that needs transaction support
type EnableTxer interface {
	// EnableTx enables transaction, basically it replaces the underling database handle sql.DB with sql.Tx
	EnableTx(dataInterface TxDataInterface)
}


// UserDataInterface represents interface for user data access through database
type UserDataInterface interface {
...
	Update(user *model.User) (rowsAffected int64, err error)
	// Insert adds a user to a database. The returned resultUser has a Id, which is auto generated by database
	Insert(user *model.User) (resultUser *model.User, err error)
	// Need to add this for transaction support
	EnableTxer
}