> I think this is due to the go runtime allocating an OS thread for each goro as it goes through the socket close() blocking call. I think it has to do this to maintain concurrency

I highly doubt that it is creating a thread per goro on client disconnect. If you have a minimalish example of this, the golang mailing list would be very interested in working with you to identify what went wrong and create a patch if it is an issue with the Go implementation.