sse mvc session close sync when complete or timeout.

Author: taobaorun

mcp-spring/mcp-spring-webmvc/src/main/java/io/modelcontextprotocol/server/transport/WebMvcSseServerTransportProvider.java

@@ -264,11 +264,13 @@ private ServerResponse handleSseConnection(ServerRequest request) {
 			sseBuilder.onComplete(() -> {
 				logger.debug("SSE connection completed for session: {}", sessionId);
 				// explicitly close the session when the SSE connection is completed
-				session.closeGracefully().doOnSuccess(v -> sessions.remove(sessionId)).subscribe();
+				session.close();
+				sessions.remove(sessionId);
 			});
 			sseBuilder.onTimeout(() -> {
 				logger.debug("SSE connection timed out for session: {}", sessionId);
-				session.closeGracefully().doOnSuccess(v -> sessions.remove(sessionId)).subscribe();
+				session.close();
+				sessions.remove(sessionId);
 			});
 			this.sessions.put(sessionId, session);