Taking inspiration from
https://github.com/golang/go/issues/17604#issuecomment-256384471
suggests that taking the address of a stack variable for use in atomics
works (at least, the race detector doesn't complain) but is doing it
wrong.
The only other change is a change in Leader() detecting if HA is enabled
to fast-path out. This value never changes after NewCore, so we don't
need to grab the read lock to check it.
8916f6b625