Although #6771 significantly cleaned up how gRPC services stop and clean
up, it didn't make any changes to our HTTP servers or our non-server
(e.g. crl-updater, log-validator) processes. This change finishes the
work.
Add a new helper method cmd.WaitForSignal, which simply blocks until one
of the three signals we care about is received. This easily replaces all
calls to cmd.CatchSignals which passed `nil` as the callback argument,
with the added advantage that it doesn't call os.Exit() and therefore
allows deferred cleanup functions to execute. This new function is
intended to be the last line of main(), allowing the whole process to
exit once it returns.
Reimplement cmd.CatchSignals as a thin wrapper around cmd.WaitForSignal,
but with the added callback functionality. Also remove the os.Exit()
call from CatchSignals, so that the main goroutine is allowed to finish
whatever it's doing, call deferred functions, and exit naturally.
Update all of our non-gRPC binaries to use one of these two functions.
The vast majority use WaitForSignal, as they run their main processing
loop in a background goroutine. A few (particularly those that can run
either in run-once or in daemonized mode) still use CatchSignals, since
their primary processing happens directly on the main goroutine.
The changes to //test/load-generator are the most invasive, simply
because that binary needed to have a context plumbed into it for proper
cancellation, but it already had a custom struct type named "context"
which needed to be renamed to avoid shadowing.
Fixes https://github.com/letsencrypt/boulder/issues/6794
bd1d27b8e8