.github/workflows: use ubuntu-latest (#2)

diff --git a/.github/workflows/go_test.yml b/.github/workflows/go_test.yml
index 4e94690..aea7c28 100644
--- a/.github/workflows/go_test.yml
+++ b/.github/workflows/go_test.yml
@@ -7,7 +7,7 @@
   pull_request:
 jobs:
   test:
-    runs-on: "linux-x64-ubuntu-latest-64-core"
+    runs-on: "ubuntu-latest"
     steps:
       - uses: actions/checkout@master