Upon calling fooInformer.Informer().GetStore().Resync() you are using Resync function/method of the Store type defined in: client-go/tools/cache/store.go

And there we can see the following:

In the Store type definition:

// Resync is meaningless in the terms appearing here but has
// meaning in some implementations that have non-trivial
// additional behavior (e.g., DeltaFIFO).
Resync() error

And in the Resync definition further below:

// Resync is meaningless for one of these
func (c *cache) Resync() error {
return nil
}

Unless you actually have some other class to do the Resync, this is supposed to really do nothing.

That is why

The call succeeds, but the resync is not happening.

Hope that helps!