Add finalizer to zstd.

[cyriltovena]

Fixes #3305

Signed-off-by: Cyril Tovena cyril.tovena@gmail.com

[kavirajk]

Would be nice to lock the behaviour via test somehow!

[cyriltovena]

Would be nice to lock the behaviour via test somehow!

Yes I didn't how, you have an idea ?

[kavirajk]

Yes I didn't how, you have an idea ?

Neither do I :P

Quickly checked the runtime package and found this

https://github.com/golang/go/blob/master/src/runtime/mfinal_test.go#L47-L71. Looks like we can trigger it via runtime.GC(). may be something similar we can do?

[cyriltovena]

yeah I can trigger it for sure but how can I verify it was triggered :)

[kavirajk]

how can I verify it was triggered :)

I'm thinking something like this

func (z *zfsReader) Close() {
	z.ch <- struct{}{}
}

// do something with the reader

<-done
runtime.GC()
select {
	case <-z.ch:
	case <-time.After(time.Second * 4):
		t.Errorf("finalizer didn't run")
	}
}

[owen-d]

@kavirajk has a nice test suggestion to add :)