Should here return `context.Cause(ctx)` or the error warp with `context.Cause(ctx)` when `ctx.Done()` ? about redislock

[spike014]

context.Cause(ctx) and WithCancelCause is new after Go1.20.

I think the issue should return to :

Should here return ctx.Err() or the error warp with ctx.Err() when ctx.Done() ?

The ctx may with timeout setting.
I think here may let user know why he/she didn't get the lock when the ctx's deadline passes or canceled by someone.
Then the error can be deal with the way like this:

if err == context.DeadlineExceeded {
    log.Println("context timeout error", err)
    // or do something else
    // Timeout~
} else if err == context.Canceled {
    // Oh! Somebody cancaled this context. That is NOT the error from `bsm/redislock`.
}

[dim]

Will continue in #64, thanks for pointing this out