select code in the second part of your question is what the code in the
Connect method might look like. There it is checking whether the
ctx.Done() is ready to send. If it is, then the context was cancelled either because the timeout occurred, or because
cancel() was called.
errors are values. Treat them as such. If it is important for you to understand the cause of the error (network down? unexpected data? timeout?) then you should do the check and act accordingly. If recovery from the error regardless of the cause is the same, then checking the error is not as important.