add sync mode for subscription events

README.md

@@ -590,7 +590,9 @@ client.
 	WithExitWhenNoSubscription(false).
 	// WithRetryStatusCodes allow retry the subscription connection when receiving one of these codes
 	// the input parameter can be number string or range, e.g 4000-5000
-	WithRetryStatusCodes("4000", "4000-4050")
+	WithRetryStatusCodes("4000", "4000-4050").
+	// WithSyncMode subscription messages are executed in sequence (without goroutine)
+	WithSyncMode(true)
 ```
 
 #### Subscription Protocols

subscription.go

@@ -364,6 +364,7 @@ type SubscriptionClient struct {
 	onError                func(sc *SubscriptionClient, err error) error
 	errorChan              chan error
 	exitWhenNoSubscription bool
+	syncMode               bool
 	keepAliveInterval      time.Duration
 	retryDelay             time.Duration
 	mutex                  sync.Mutex
@@ -464,6 +465,12 @@ func (sc *SubscriptionClient) WithExitWhenNoSubscription(value bool) *Subscripti
 	return sc
 }
 
+// WithSyncMode subscription messages are executed in sequence (without goroutine)
+func (sc *SubscriptionClient) WithSyncMode(value bool) *SubscriptionClient {
+	sc.syncMode = value
+	return sc
+}
+
 // Keep alive subroutine to send ping on specified interval
 func startKeepAlive(ctx context.Context, c WebsocketConn, interval time.Duration) {
 	ticker := time.NewTicker(interval)
@@ -806,13 +813,20 @@ func (sc *SubscriptionClient) Run() error {
 				if sub == nil {
 					sub = &Subscription{}
 				}
-				go func() {
+
+				execMessage := func() {
 					if err := sc.protocol.OnMessage(subContext, *sub, message); err != nil {
 						sc.errorChan <- err
 					}
 
 					sc.checkSubscriptionStatuses(subContext)
-				}()
+				}
+
+				if sc.syncMode {
+					execMessage()
+				} else {
+					go execMessage()
+				}
 			}
 		}
 	}()

subscription_test.go

@@ -13,7 +13,8 @@ import (
 	"nhooyr.io/websocket"
 )
 
-func TestSubscription_LifeCycleEvents(t *testing.T) {
+func testSubscription_LifeCycleEvents(t *testing.T, syncMode bool) {
+
 	server := subscription_setupServer(8082)
 	client, subscriptionClient := subscription_setupClients(8082)
 	msg := randomID()
@@ -84,6 +85,7 @@ func TestSubscription_LifeCycleEvents(t *testing.T) {
 	subscriptionClient = subscriptionClient.
 		WithExitWhenNoSubscription(false).
 		WithTimeout(3 * time.Second).
+		WithSyncMode(syncMode).
 		OnConnected(func() {
 			lock.Lock()
 			defer lock.Unlock()
@@ -200,6 +202,14 @@ func TestSubscription_LifeCycleEvents(t *testing.T) {
 	}
 }
 
+func TestSubscription_LifeCycleEvents(t *testing.T) {
+	testSubscription_LifeCycleEvents(t, false)
+}
+
+func TestSubscription_WithSyncMode(t *testing.T) {
+	testSubscription_LifeCycleEvents(t, true)
+}
+
 func TestSubscription_WithRetryStatusCodes(t *testing.T) {
 	stop := make(chan bool)
 	msg := randomID()