PUB / SUB sockets

[samsamfire]

Hello, First of all, super cool to see a pure golang implementation of zeroMQ, great work ! I've encountered issues with the PUB socket. I don't know exactly what triggers the problem but if i connect / disconnect a couple of subscribers sometimes i stop receiving anything on the subscriber side, and if I restart the publisher then it starts working again. I've tested this with the pyzmq python package on the receiver end. When this issue occurs, I also get a memory leak on the publisher side because the high watermark is by default set to 0 which apparently means no limit, which causes the send buffer to grow indefinitely. ==> I think this is probably not a good default behavior.