Added: creating database, sql tx repository

internal/db/irepository.go

@@ -0,0 +1,14 @@
+package db
+
+import "database/sql"
+
+type ITxRepository interface {
+	// Creates a new tx.
+	Begin() (*sql.Tx, error)
+
+	// Rollbacks tx's data or returns an error to the given error's pointer address.
+	RollbackOnError(*sql.Tx, *error)
+
+	// Applies changes to the database.
+	Commit(*sql.Tx) error
+}