MessageSessionClient.Close can panic on nil session

[coolguy1771]

Bug

Close() currently panics if called when a session hasn't been established (e.g., if session creation failed during initialization). The method attempts to access c.session.SessionID without verifying that c.session is non-nil.

Fix

Added a guard clause to return an error instead of panicking when the session is nil.

func (c *MessageSessionClient) Close(ctx context.Context) error {
    c.mu.Lock()
    defer c.mu.Unlock()
    
    if c.session == nil {
        return fmt.Errorf("cannot close: no active session found")
    }
    
    return c.deleteMessageSession(ctx, c.scaleSetID, c.session.SessionID)
}

Test Case

Verified the fix with the following unit test:

func TestMessageSessionClient_Close_NilSession(t *testing.T) {
    client := &MessageSessionClient{session: nil}
    err := client.Close(context.Background())
    
    if err == nil {
        t.Fatal("expected error when closing nil session, got nil")
    }
    if !strings.Contains(err.Error(), "no active session") {
        t.Errorf("unexpected error message: %v", err)
    }
}