Describe the bug

gh cs ports forward crashes with a Go runtime fatal error (concurrent map writes) when forwarding multiple ports simultaneously. This is a race condition where multiple goroutines write to an unsynchronized map concurrently.

Steps to reproduce

1. Have a running codespace
2. Forward multiple ports in a single command:

   gh cs ports forward 80:80 8080:8080 3930:3930 -c <codespace-name>
   

3. The command crashes intermittently

Expected vs actual behavior

Expected: All ports forward successfully.

Actual: The process crashes. On repeated attempts, different errors surface:

• fatal error: concurrent map writes (race condition, most common)
• error forwarding port: create tunnel port failed: ... 400: Bad Request
• error connecting to tunnel: ... ssh: rejected: connect failed (Connection refused)

Stack trace

goroutine 99 [running]:
github.com/microsoft/dev-tunnels/go/tunnels.(*Manager).CreateTunnelPort(...)
    github.com/microsoft/dev-tunnels@v0.1.19/go/tunnels/manager.go:452 +0xcc
github.com/cli/cli/v2/internal/codespaces/portforwarder.(*CodespacesPortForwarder).ForwardPort(...)
    .../port_forwarder.go:164 +0x280
github.com/cli/cli/v2/pkg/cmd/codespace.(*App).ForwardPorts.func1()
    .../codespace/ports.go:349 +0x25c
golang.org/x/sync/errgroup.(*Group).Go.func1()

Possible cause

ports.go:349 launches concurrent goroutines via errgroup.Go for each port. These all call CreateTunnelPort on the same Manager instance, which writes to a shared map without synchronization.