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

Lines 88 to 93 in 9348b33

    
           select { 
        
           case <-ctx.Done(): 
        
           	return nil, ErrNotObtained 
        
           case <-ticker.C: 
        
           }

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

Because ctx may contain the CancelCause which inside the user's parent context generated by context.WithCancelCause.

I will contribute a PR later. If there is any problem, please let me know.

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`.
}

Will continue in #64, thanks for pointing this out


	select {
	case <-ctx.Done():
	return nil, ErrNotObtained
	case <-ticker.C:
	}