fix: resolve test race conditions and update golangci-lint action

- Fix race condition in gateway tests by using TestMain to set Gin mode once
  - Remove duplicate gin.SetMode(gin.TestMode) calls from individual tests
  - Add TestMain function to initialize test environment before all tests
  - Prevents race conditions when tests run in parallel with -race flag

- Update golangci-lint-action from v6 to v7
  - v6 doesn't support golangci-lint v2.x versions
  - v7 supports golangci-lint v2.x and automatically selects compatible version
  - Change version from v2.6.0 to latest for automatic compatibility

All tests now pass with race detector enabled.

services/gateway/gateway_test.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"testing"
 	"time"
 
@@ -18,11 +19,17 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+// TestMain sets up the test environment before running tests.
+func TestMain(m *testing.M) {
+	// Set Gin to test mode once for all tests to avoid race conditions
+	gin.SetMode(gin.TestMode)
+	// Run tests
+	os.Exit(m.Run())
+}
+
 func TestNewGateway(t *testing.T) {
 	t.Parallel()
 
-	gin.SetMode(gin.TestMode)
-
 	tests := []struct {
 		name    string
 		cfg     config.ConfigProvider
@@ -70,8 +77,6 @@ func TestNewGateway(t *testing.T) {
 func TestGateway_SetupRoutes(t *testing.T) {
 	t.Parallel()
 
-	gin.SetMode(gin.TestMode)
-
 	tests := []struct {
 		name           string
 		routes         []RouteConfig
@@ -127,8 +132,6 @@ func TestGateway_SetupRoutes(t *testing.T) {
 func TestGateway_handleRoute(t *testing.T) {
 	t.Parallel()
 
-	gin.SetMode(gin.TestMode)
-
 	tests := []struct {
 		name           string
 		route          RouteConfig
@@ -199,8 +202,6 @@ func TestGateway_handleRoute(t *testing.T) {
 func TestGateway_handleRoute_AllMethods(t *testing.T) {
 	t.Parallel()
 
-	gin.SetMode(gin.TestMode)
-
 	methods := []string{
 		http.MethodGet,
 		http.MethodPost,
@@ -271,8 +272,6 @@ func TestLoadRoutes(t *testing.T) {
 func TestGateway_NoRoute(t *testing.T) {
 	t.Parallel()
 
-	gin.SetMode(gin.TestMode)
-
 	gateway := &Gateway{
 		config:        &mockConfigProvider{},
 		log:           &mockLogger{},