Exposing lock age

[josegonzalez]

I'm not sure if this is possible, but I'd be happy to try and help implement it if it's feasible.

My use case is in dokku, where we use this to ensure there aren't concurrent mutations of the docker state by ps:retire (since the command happens in the background). I'd like to be able to somehow detect that the lock is ancient and then delete the lock in that case (or at least exit with a different exit code). Right now, we don't have a file handle exposed via api that I could use to detect this and I'm looking for the "correct" way to do it if it is at all possible.