Add timeout to unix socket connection

[jn9e9]

rust client has a timout on the unix socket connection (of configurable length) which allows the client application to recover (i.e. detect failure and compensate if possible) if the parsec daemon is not responding. Go client needs same functionality - default of 1s likely sensible.

[jn9e9]

will need ability to mock the parsec service at the unix socket level, so will depend on #19

[jn9e9]

For dialling, we should be able to use a dialler with a context, having deadline set: https://pkg.go.dev/net#Dialer
For individual reads/writes, we'll have to set deadlines on each read/write for the timeout period - this is ok because the client should only be used single threaded (i.e. one request/response in flight at once), so we'll never get overlapping call windows messing up the deadlines. go doesn't let us set timeouts per read/write, just read and write deadlines on the connection as a whole