Fix cloud build by updating to go 1.13
Fix cloud build by updating to go 1.13

Change-Id: I08d9a4b44d6835b9e82167e58c35134e6e453e76
NOTRY=true
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/260820
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot