ci: add TEST_DB_HOST env var for service container connectivity

backend/testutils/testdb/testdb.go

@@ -29,6 +29,13 @@ const (
 	adminDatabaseDSN = "postgres://myuser:mypassword@localhost:5432/mydb?sslmode=disable"
 )
 
+func dbHost() string {
+	if h := os.Getenv("TEST_DB_HOST"); h != "" {
+		return h
+	}
+	return "localhost"
+}
+
 // CreateTestDatabase creates a fresh isolated test database, runs the schema migration,
 // and returns a pool connected to it. If a database with the same name exists, it's
 // dropped first. This enables parallel test execution across packages since each
@@ -36,7 +43,8 @@ const (
 func CreateTestDatabase(dbName string) *pgxpool.Pool {
 	ctx := context.Background()
 
-	adminPool, err := pgxpool.New(ctx, adminDatabaseDSN)
+	adminDSN := fmt.Sprintf("postgres://myuser:mypassword@%s:5432/mydb?sslmode=disable", dbHost())
+	adminPool, err := pgxpool.New(ctx, adminDSN)
 	if err != nil {
 		log.Fatalf("testdb: failed to connect to admin database: %v", err)
 	}
@@ -68,7 +76,7 @@ func CreateTestDatabase(dbName string) *pgxpool.Pool {
 	}
 	adminPool.Close()
 
-	testDSN := fmt.Sprintf("postgres://myuser:mypassword@localhost:5432/%s?sslmode=disable", dbName)
+	testDSN := fmt.Sprintf("postgres://myuser:mypassword@%s:5432/%s?sslmode=disable", dbHost(), dbName)
 	poolCfg, err := pgxpool.ParseConfig(testDSN)
 	if err != nil {
 		log.Fatalf("testdb: failed to parse config: %v", err)
@@ -105,7 +113,8 @@ func DestroyTestDatabase(pool *pgxpool.Pool, dbName string) {
 	}
 
 	ctx := context.Background()
-	adminPool, err := pgxpool.New(ctx, adminDatabaseDSN)
+	adminDSN := fmt.Sprintf("postgres://myuser:mypassword@%s:5432/mydb?sslmode=disable", dbHost())
+	adminPool, err := pgxpool.New(ctx, adminDSN)
 	if err != nil {
 		log.Printf("testdb: warning: failed to connect to drop %s: %v", dbName, err)
 		return