With a full attach, each attach was leaking 4 goroutines. This updates attach to use errgroup instead of the hodge-podge of waitgroups and channels. In addition, the detach event was never being sent. Signed-off-by: Brian Goff <cpuguy83@gmail.com> Upstream-commit: 0f5147701775a6c5d4980a7b7c0ed2e830688034 Component: engine