fix: remove parallel execution from Gin tests to prevent data races

- Remove t.Parallel() from tests that use gin.SetMode()
  - gin.SetMode() modifies global state and is not thread-safe
  - Tests affected:
    * TestRequestIDMiddleware_GenerateNewID
    * TestRequestIDMiddleware_UseExistingID
    * TestLoggingMiddleware
    * TestLoggingMiddleware_WithRequestID
    * TestRequestIDMiddleware_MultipleRequests

- Add comments explaining why these tests cannot run in parallel
- All tests now pass with race detector enabled (-race flag)

This fixes data race warnings that were occurring when running tests
with the race detector, specifically when multiple tests tried to set
Gin's mode concurrently.

internal/logger/middleware_test.go

@@ -11,8 +11,7 @@ import (
 )
 
 func TestRequestIDMiddleware_GenerateNewID(t *testing.T) {
-	t.Parallel()
+	// Cannot run in parallel: gin.SetMode() modifies global state
-
 	gin.SetMode(gin.TestMode)
 	router := gin.New()
 	router.Use(RequestIDMiddleware())
@@ -41,8 +40,7 @@ func TestRequestIDMiddleware_GenerateNewID(t *testing.T) {
 }
 
 func TestRequestIDMiddleware_UseExistingID(t *testing.T) {
-	t.Parallel()
+	// Cannot run in parallel: gin.SetMode() modifies global state
-
 	gin.SetMode(gin.TestMode)
 	router := gin.New()
 	router.Use(RequestIDMiddleware())
@@ -196,7 +194,7 @@ func TestUserIDFromContext(t *testing.T) {
 }
 
 func TestLoggingMiddleware(t *testing.T) {
-	t.Parallel()
+	// Cannot run in parallel: gin.SetMode() modifies global state
 
 	// Create a mock logger that records log calls
 	mockLog := &mockLoggerForMiddleware{}
@@ -238,7 +236,7 @@ func TestLoggingMiddleware(t *testing.T) {
 }
 
 func TestLoggingMiddleware_WithRequestID(t *testing.T) {
-	t.Parallel()
+	// Cannot run in parallel: gin.SetMode() modifies global state
 
 	// Create a mock logger
 	mockLog := &mockLoggerForMiddleware{}
@@ -272,8 +270,7 @@ func TestLoggingMiddleware_WithRequestID(t *testing.T) {
 }
 
 func TestRequestIDMiddleware_MultipleRequests(t *testing.T) {
-	t.Parallel()
+	// Cannot run in parallel: gin.SetMode() modifies global state
-
 	gin.SetMode(gin.TestMode)
 	router := gin.New()
 	router.Use(RequestIDMiddleware())