This issue is triggered due to the `Service.Close()` call after the
go-routine for the event service exists. It is possible that during this
period a recently added subscriber with `pendingOpAdd` gets cancelled
and closed.
However, the subscriber later also enqueues a `pendingOpRemove` which
gets processed again with a call in `user.eventService.Close()` leading
to the double close panic.
This patch simply removes the `s.Close()` from the service, and leaves
the cleanup to called externally from user.Close() or user.Logout().
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