THRIFT-5240: Do connectivity check in Go server

Client: go

In compiler generated TProcessorFunction implementations, add a
goroutine after read the request to do connectivity check on the input
transport. If the transport is no longer open, cancel the context object
passed into the handler implementation.

Also define ErrAbandonRequest error, to help TSimpleServer closing
client connections that's already closed on the other end.
4 files changed