support db migrations

cmd/migrator/main.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"os/signal"
+
+	"github.com/golang-migrate/migrate/v4"
+
+	// Use it to append postgres sql and file drivers.
+	_ "github.com/golang-migrate/migrate/v4/database/postgres"
+	_ "github.com/golang-migrate/migrate/v4/source/file"
+)
+
+func main() {
+	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
+	defer cancel()
+
+	err := app(ctx)
+	if err != nil {
+		log.Fatalf("unable to run app: %v", err)
+	}
+}
+
+func app(_ context.Context) (err error) {
+	const filepath = "file:///app/db/migrations"
+	pgdsn := os.Getenv("DEVSIM_PG_DSN")
+	if pgdsn == "" {
+		return nil
+	}
+
+	filedsn := os.Getenv("DEVSIM_PG_MIGRATION")
+	if filedsn == "" {
+		filedsn = filepath
+	}
+
+	log.Println("going to apply migrations from path: " + filedsn)
+	migrations, err := migrate.New(
+		filedsn,
+		pgdsn,
+	)
+	if err != nil {
+		return fmt.Errorf("making migrator: %w", err)
+	}
+
+	defer func() {
+		sourceErr, dbErr := migrations.Close()
+		err = errors.Join(err, sourceErr, dbErr)
+	}()
+
+	version, dirty, err := migrations.Version()
+	if errors.Is(err, migrate.ErrNilVersion) {
+		log.Println("no migrations applied to database")
+	} else if err != nil {
+		return fmt.Errorf("getting version: %w", err)
+	} else {
+		log.Printf("current migration version: %d (dirty: %t)", version, dirty)
+	}
+
+	err = migrations.Up()
+	if err != nil {
+		return fmt.Errorf("applying migrations: %w", err)
+	}
+
+	version, dirty, err = migrations.Version()
+	if errors.Is(err, migrate.ErrNilVersion) {
+		log.Println("no migrations applied to database")
+	} else if err != nil {
+		return fmt.Errorf("getting version: %w", err)
+	} else {
+		log.Printf("updated to migration version: %d (dirty: %t)", version, dirty)
+	}
+
+	return nil
+}