db.go

// General ideas:
// - A project hides SQL in custom db package and exposes CRUD methods
// - I can generate that db package interface with protoc
// - time.Time has to be converted into timestamp.Timestamp for a gRPC service to use the value
// - database/sql writes to a time.Time and I convert that into timestamp.Timestamp.
//   All conversions are kept in a single package.
// - gRPC has error types that map to SQL errors such as not found, already exists, etc.
// - database/sql will only write a timestamp to `time.Time`
// - I map errors like sql.ErrNoRows to gRPC's equivalent

// ----

// package pb
// A regular gRPC server interface
type DBServer interface {
	CreateAccount(context.Context, *CreateAccountRequest) (*CreateAccountResponse, error)
}

// ----

// package db
// A DB/gRPC interface
type DB interface {
	pb.DBServer
	WithTx() (pb.DBServer, Tx, error)
}

type Tx interface {
	Commit() error
	Rollback() error
}

// New takes an SQL connection returns a DB which is the implemented pb.DBServer with an additional method WithTx().
// WithTx() returns a pb.DBServer because you cannot create nested transactions.
func New(*sql.DB) DB {
  // ...
}