How to Properly Clean Up Application State When Server Disconnects or Closes? (STDIO)

[Mr-Yaya]

Pre-submission Checklist

• I have checked that this question would not be more appropriate as an issue in a specific repository
• I have searched existing discussions and documentation for answers

Question Category

• Protocol Specification
• SDK Usage
• Server Implementation
• General Implementation
• Documentation
• Other

Your Question

Hi all,

I’m working with the Go SDK and the MCP protocol, and I’m trying to ensure my application state is properly cleaned up when the server disconnects or closes. Here’s a simplified version of my code:

func (s *Server) Run() error {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	serverErrChan := make(chan error, 1)
	go func() {
		serverErrChan <- s.Server.Run(ctx, &mcp.StdioTransport{}) // Run using the mcp go sdk
	}()

	s.start3pApplication()
	defer s.stop3pApplication()

	exitChan := make(chan os.Signal, 2)
	signal.Notify(exitChan, os.Interrupt, syscall.SIGTERM)

	select {
	case <-exitChan:
		return nil
	case err := <-serverErrChan:
		if err != nil && err != context.Canceled {
			return err
		}
		return nil
	}
}

Problem:
When I run this with go run and hit Ctrl+C, everything works as expected: stop3pApplication is called and cleanup happens.
However, when I run the same code via Claude Desktop or the MCP Inspector, stop3pApplication is never called. I suspect these tools are handling disconnects differently (not sending a signal?), so my cleanup code in defer isn’t triggered.

Question:

• How can I reliably detect when the connection is closed or the server is disconnected, especially in these environments?
• Is there a better way to ensure that stop3pApplication is always called, regardless of how the server is stopped/disconnected?
• Are there any best practices or examples for handling cleanup in this kind of context/protocol setup?
  Any advice or pointers would be greatly appreciated!