fix panic on shutdown caused by double channel close (#209)

service.go

@@ -99,6 +99,7 @@ type service struct {
 	done chan struct{}
 	opts Options
 	sync.RWMutex
+	stopped bool
 }
 
 // NewService creates and returns a new Service based on the packages within.
@@ -424,7 +425,7 @@ func (s *service) Stop() error {
 		}
 	}
 
-	close(s.done)
+	s.notifyShutdown()
 
 	return nil
 }
@@ -448,10 +449,23 @@ func (s *service) Run() error {
 		return err
 	}
 
-	// wait on context cancel
 	<-s.done
 
-	return s.Stop()
+	return nil
+}
+
+// notifyShutdown marks the service as stopped and closes the done channel.
+// It ensures the channel is closed only once, preventing multiple closures.
+func (s *service) notifyShutdown() {
+	s.Lock()
+	if s.stopped {
+		s.Unlock()
+		return
+	}
+	s.stopped = true
+	s.Unlock()
+
+	close(s.done)
 }
 
 type Namer interface {

service_test.go

@@ -3,7 +3,9 @@ package micro
 import (
 	"reflect"
 	"testing"
+	"time"
 
+	"github.com/stretchr/testify/require"
 	"go.unistack.org/micro/v4/broker"
 	"go.unistack.org/micro/v4/client"
 	"go.unistack.org/micro/v4/config"
@@ -737,3 +739,41 @@ func Test_getNameIndex(t *testing.T) {
 	}
 }
 */
+
+func TestServiceShutdown(t *testing.T) {
+	defer func() {
+		if r := recover(); r != nil {
+			t.Fatalf("service shutdown failed: %v", r)
+		}
+	}()
+
+	s, ok := NewService().(*service)
+	require.NotNil(t, s)
+	require.True(t, ok)
+
+	require.NoError(t, s.Start())
+	require.False(t, s.stopped)
+
+	require.NoError(t, s.Stop())
+	require.True(t, s.stopped)
+}
+
+func TestServiceMultipleShutdowns(t *testing.T) {
+	defer func() {
+		if r := recover(); r != nil {
+			t.Fatalf("service shutdown failed: %v", r)
+		}
+	}()
+
+	s := NewService()
+
+	go func() {
+		time.Sleep(10 * time.Millisecond)
+		// first call
+		require.NoError(t, s.Stop())
+		// duplicate call
+		require.NoError(t, s.Stop())
+	}()
+
+	require.NoError(t, s.Run())
+}