diff --git a/auth/example/main.go b/auth/example/main.go
index 4d416b3..251d3b1 100644
--- a/auth/example/main.go
+++ b/auth/example/main.go
@@ -9,6 +9,9 @@ import (
 
 	"github.com/go-gost/plugin/auth/proto"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/status"
 )
 
 var (
@@ -20,6 +23,11 @@ type server struct {
 }
 
 func (s *server) Authenticate(ctx context.Context, in *proto.AuthenticateRequest) (*proto.AuthenticateReply, error) {
+	token := s.getCredentials(ctx)
+	if token != "gost" {
+		return nil, status.Error(codes.Unauthenticated, codes.Unauthenticated.String())
+	}
+
 	reply := &proto.AuthenticateReply{}
 	if in.GetUsername() == "gost" && in.GetPassword() == "gost" {
 		reply.Ok = true
@@ -28,6 +36,14 @@ func (s *server) Authenticate(ctx context.Context, in *proto.AuthenticateRequest
 	return reply, nil
 }
 
+func (s *server) getCredentials(ctx context.Context) string {
+	md, ok := metadata.FromIncomingContext(ctx)
+	if ok && len(md["token"]) > 0 {
+		return md["token"][0]
+	}
+	return ""
+}
+
 func main() {
 	flag.Parse()
 	lis, err := net.Listen("tcp", fmt.Sprintf(":%d", *port))