There is a cleanup function deferred to remove the provider from the global
provider map. However, this function didn't bind the value of provider ahead of
time, so when the provider creation returned with nil for provider, we tried to
cleanup a nil provider, and panicked.
Previously, the only constructor for the etwlogrus hook accepted a name, and
created a new ETW provider with that name. With this change, there is another
constructor which takes an already created ETW provider. This is to allow the
use of the ETW provider for other things, such as if the application wants to
support ETW capture state.
ETW and Logrus have similar, but different definitiosn of log level.
Originally, the plan was to just convert the integer value of the Logrus level
to an ETW level, and leave it at that. However, it turns out there are tools
that assume you are logging with the standard set of ETW log level. So now we
will map the Logrus level to an ETW level, so that these tools better.
Kevin Parsons