The docs say:
Note that while correct uses of TryLock do exist, they are rare,
and use of TryLock is often a sign of a deeper problem in a particular use of mutexes.
Rare code! Or bad code! Who can tell!
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
This allows us to check lock invariants.
It was proposed upstream and rejected in:
https://github.com/golang/go/issues/1366
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
