fix(migrate): validate migration directory before provider creation

migrate/migrate.go

@@ -15,6 +15,7 @@ import (
 
 // New returns a provider for SQL files in dir and optional provider-local Go
 // migrations. Pass "." for files at the embedded root and a nonnil logger.
+// The selected directory must exist, including when using only Go migrations.
 // Construction does not connect to db; the caller owns and closes db.
 //
 // PostgreSQL uses Goose's session advisory locker with its default lock ID and
@@ -36,6 +37,13 @@ func New(db *sql.DB, dialect goose.Dialect, files embed.FS, dir string, logger *
 	if err != nil {
 		return nil, fmt.Errorf("migrate: directory %q: %w", dir, err)
 	}
+	info, err := fs.Stat(root, ".")
+	if err != nil {
+		return nil, fmt.Errorf("migrate: directory %q: %w", dir, err)
+	}
+	if !info.IsDir() {
+		return nil, fmt.Errorf("migrate: directory %q: not a directory", dir)
+	}
 	opts := []goose.ProviderOption{
 		goose.WithDisableGlobalRegistry(true),
 		goose.WithGoMigrations(migrations...),