periodic state exchange in go

Very simple eventual-delivery of absolute state over tcp.

a simple client/server that handles reconnects under the hood but not redelivery, since the intent is to be used for absolute state, where redelivering outdated messages would be pointless.

• aggressive timeouts
• automatically reconnects on failure
• Read() will always succeed eventually, but might have missed some messages in the middle
• Write() will usually succeed eventually, but doesn't guarantee the receiver actually read the message