fix: reject closing already closed lifecycle

internal/session/lifecycle/lifecycle.go

@@ -80,6 +80,12 @@ func (l *lifecycle) User() string {
 func (l *lifecycle) SetChannel(channel ssh.Channel) error {
 	l.mu.Lock()
 	defer l.mu.Unlock()
+	if l.status == types.SessionStatusCLOSED {
+		return fmt.Errorf("lifecycle is closed")
+	}
+	if channel == nil {
+		return fmt.Errorf("channel cannot be nil")
+	}
 	if l.channel != nil {
 		return fmt.Errorf("channel already set")
 	}
@@ -100,6 +106,9 @@ func (l *lifecycle) Connection() ssh.Conn {
 func (l *lifecycle) SetStatus(status types.SessionStatus) {
 	l.mu.Lock()
 	defer l.mu.Unlock()
+	if l.status == types.SessionStatusCLOSED {
+		return
+	}
 	l.status = status
 	if status == types.SessionStatusRUNNING && l.startedAt.IsZero() {
 		l.startedAt = time.Now()
@@ -114,41 +123,41 @@ func (l *lifecycle) IsActive() bool {
 
 func (l *lifecycle) Close() error {
 	l.mu.Lock()
-	defer l.mu.Unlock()
-
 	if l.status == types.SessionStatusCLOSED {
-		return l.closeErr
+		closeErr := l.closeErr
+		l.mu.Unlock()
+		return closeErr
 	}
 	l.status = types.SessionStatusCLOSED
 
+	channel := l.channel
+	conn := l.conn
+	l.mu.Unlock()
+
 	var errs []error
-	errs = append(errs, l.closeChannel())
-	errs = append(errs, l.closeConnection())
+	if channel != nil {
+		if err := channel.Close(); err != nil && !isClosedError(err) {
+			errs = append(errs, err)
+		}
+	}
+	if conn != nil {
+		if err := conn.Close(); err != nil && !isClosedError(err) {
+			errs = append(errs, err)
+		}
+	}
+
 	l.cleanupRegistry()
-	errs = append(errs, l.cleanupForwarder())
+	if err := l.cleanupForwarder(); err != nil {
+		errs = append(errs, err)
+	}
 
-	l.closeErr = errors.Join(errs...)
-	return l.closeErr
-}
+	closeErr := errors.Join(errs...)
 
-func (l *lifecycle) closeChannel() error {
-	if l.channel == nil {
-		return nil
-	}
-	if err := l.channel.Close(); err != nil && !isClosedError(err) {
-		return err
-	}
-	return nil
-}
+	l.mu.Lock()
+	l.closeErr = closeErr
+	l.mu.Unlock()
 
-func (l *lifecycle) closeConnection() error {
-	if l.conn == nil {
-		return nil
-	}
-	if err := l.conn.Close(); err != nil && !isClosedError(err) {
-		return err
-	}
-	return nil
+	return closeErr
 }
 
 func (l *lifecycle) cleanupRegistry() {