fix: handle closed HTTP/2 sessions after GOAWAY

[mcollina]

Summary

Fixes issue #409 where HTTP/2 sessions would get stuck after receiving a GOAWAY frame from the server.

Changes

• Updated to check for both and HTTP/2 session states
• Added proper cleanup of closed sessions before creating new ones
• Added comprehensive test case in to reproduce the GOAWAY scenario

Problem Description

When an HTTP/2 server sends a GOAWAY frame, the Node.js session gets closed but not necessarily destroyed. The original code only checked , causing the proxy to get stuck using a closed session that cannot accept new streams.

This resulted in all subsequent requests failing with errors, particularly affecting long-running connections like GraphQL subscriptions.

Solution

Changed the session check from:

if (!http2Client || http2Client.destroyed) {

to:

if (!http2Client || http2Client.destroyed || http2Client.closed) {
  if (http2Client && !http2Client.destroyed) http2Client.destroy()

This ensures that:

1. Both destroyed and closed sessions are detected
2. Closed sessions are properly destroyed before creating new ones
3. New requests get fresh, working sessions

Test Plan

• Added test that simulates GOAWAY scenario using Node.js HTTP/2 server
• Verified existing HTTP/2 tests continue to pass
• Based on production-tested patch from issue reporter

Fixes #409