diff --git a/internal/service/user/user_service.go b/internal/service/user/user_service.go
index e04f238..711d151 100644
--- a/internal/service/user/user_service.go
+++ b/internal/service/user/user_service.go
@@ -8,7 +8,6 @@ import (
 	"taskflow/internal/domain/user"
 	"taskflow/internal/dto"
 	"taskflow/internal/repository/gorm/gorm_user"
-	"taskflow/pkg"
 	"taskflow/pkg/jwt"
 	"taskflow/pkg/validator"
 
@@ -17,11 +16,12 @@ import (
 )
 
 type UserService struct {
-	repo gorm_user.UserRepositoryInterface
+	repo      gorm_user.UserRepositoryInterface
+	jwtSecret []byte
 }
 
-func NewUserService(repo gorm_user.UserRepositoryInterface) *UserService {
-	return &UserService{repo: repo}
+func NewUserService(repo gorm_user.UserRepositoryInterface, jwtSecret string) *UserService {
+	return &UserService{repo: repo, jwtSecret: []byte(jwtSecret)}
 }
 
 var _ UserServiceInterface = (*UserService)(nil)
@@ -80,7 +80,7 @@ func (s *UserService) AuthenticateUser(req *dto.AuthRequest) (*dto.AuthResponse,
 		return nil, errors.New("invalid credentials")
 	}
 
-	secretKey := []byte(pkg.GetEnv("JWT_SECRET", "secret-key"))
+	secretKey := s.jwtSecret
 	token, err := jwt.CreateToken(u.ID, u.Email, secretKey)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create token: %w", err)
diff --git a/internal/service/user/user_service_test.go b/internal/service/user/user_service_test.go
index 51b134a..ed2e471 100644
--- a/internal/service/user/user_service_test.go
+++ b/internal/service/user/user_service_test.go
@@ -46,7 +46,8 @@ func TestCreateUser(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			mockRepo := new(gorm_user.MockUserRepository)
-			svc := NewUserService(mockRepo)
+			secretKey := []byte("secret")
+			svc := NewUserService(mockRepo, string(secretKey))
 
 			if tt.mockSetup != nil {
 				tt.mockSetup(mockRepo)
@@ -97,7 +98,8 @@ func TestAuthenticateUser(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			mockRepo := new(gorm_user.MockUserRepository)
-			svc := NewUserService(mockRepo)
+			secretKey := []byte("secret")
+			svc := NewUserService(mockRepo, string(secretKey))
 
 			if tt.mockSetup != nil {
 				tt.mockSetup(mockRepo)
@@ -165,7 +167,8 @@ func TestUpdatePassword(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			mockRepo := new(gorm_user.MockUserRepository)
-			svc := NewUserService(mockRepo)
+			secretKey := []byte("secret")
+			svc := NewUserService(mockRepo, string(secretKey))
 
 			if tt.mockSetup != nil {
 				tt.mockSetup(mockRepo)
@@ -209,7 +212,8 @@ func TestDeleteUser(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			mockRepo := new(gorm_user.MockUserRepository)
-			svc := NewUserService(mockRepo)
+			secretKey := []byte("secret")
+			svc := NewUserService(mockRepo, string(secretKey))
 
 			if tt.mockSetup != nil {
 				tt.mockSetup(mockRepo)
diff --git a/main.go b/main.go
index be12d06..0be0674 100644
--- a/main.go
+++ b/main.go
@@ -50,7 +50,7 @@ func main() {
 	taskRepo := gorm_task.NewTaskRepository(db)
 	taskSvc := task_service.NewTaskService(taskRepo)
 	userRepo := gorm_user.NewUserRepository(db)
-	userSvc := user_service.NewUserService(userRepo)
+	userSvc := user_service.NewUserService(userRepo, string(secretKey))
 
 	userAuth := auth.NewUserAuth(string(secretKey), userRepo)