Updating go to 1.8.1 for Mac

BUG=chromium:727089
R=kjellander@chromium.org

Review-Url: https://codereview.chromium.org/2913583002 .
diff --git a/golang/mac/go.tar.gz.sha1 b/golang/mac/go.tar.gz.sha1
index c76e704..f74b8e0 100644
--- a/golang/mac/go.tar.gz.sha1
+++ b/golang/mac/go.tar.gz.sha1
@@ -1 +1 @@
-be686ec7ba68d588735cc2094ccab8bdd651de9e
+aecf5ec9360a004fdbff181269554892743f4bf6