add ability to replace golang migration registry with custom one

migrate.go

@@ -125,20 +125,34 @@ func (ms Migrations) String() string {
 
 // AddMigration adds a migration.
 func AddMigration(up func(*sql.Tx) error, down func(*sql.Tx) error) {
-	_, filename, _, _ := runtime.Caller(1)
-	AddNamedMigration(filename, up, down)
+	AddMigrationToRegistry(registeredGoMigrations, up, down)
 }
 
 // AddNamedMigration : Add a named migration.
 func AddNamedMigration(filename string, up func(*sql.Tx) error, down func(*sql.Tx) error) {
+	AddNamedMigrationToRegistry(registeredGoMigrations, filename, up, down)
+}
+
+// AddMigration adds a migration.
+func AddMigrationToRegistry(registry map[int64]*Migration, up func(*sql.Tx) error, down func(*sql.Tx) error) {
+	_, filename, _, _ := runtime.Caller(1)
+	AddNamedMigrationToRegistry(registry, filename, up, down)
+}
+
+// AddNamedMigration : Add a named migration.
+func AddNamedMigrationToRegistry(registry map[int64]*Migration, filename string, up func(*sql.Tx) error, down func(*sql.Tx) error) {
 	v, _ := NumericComponent(filename)
 	migration := &Migration{Version: v, Next: -1, Previous: -1, Registered: true, UpFn: up, DownFn: down, Source: filename}
 
-	if existing, ok := registeredGoMigrations[v]; ok {
+	if existing, ok := registry[v]; ok {
 		panic(fmt.Sprintf("failed to add migration %q: version conflicts with %q", filename, existing.Source))
 	}
 
-	registeredGoMigrations[v] = migration
+	registry[v] = migration
+}
+
+func SetMigrationsRegistry(m map[int64]*Migration) {
+	registeredGoMigrations = m
 }
 
 func collectMigrationsFS(fsys fs.FS, dirpath string, current, target int64) (Migrations, error) {