sync: use atomic.Pointer for entry
sync: use atomic.Pointer for entry

Change-Id: Ie3b4bfe483d7ef43da29ea1dd73d423dac36cf39
Reviewed-on: https://go-review.googlesource.com/c/go/+/432055
Auto-Submit: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Reviewed-by: Cherry Mui <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
Reviewed-by: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Run-TryBot: Changkun Ou <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@changkun.de>

golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go