ci: fix CI fail (#818)

* ci: fix CI fail

* ci: fix CI fail

* ci: fix CI fail
diff --git a/.github/workflows/backend-unit-test.yml b/.github/workflows/backend-unit-test.yml
index 2595163..2a8dd83 100644
--- a/.github/workflows/backend-unit-test.yml
+++ b/.github/workflows/backend-unit-test.yml
@@ -38,9 +38,9 @@
           go-version: '1.13'
 
       - name: setup lua
-        uses: leafo/gh-actions-lua@v7
-        with:
-          luaVersion: "5.1.5"
+        run: |
+          sudo apt-get update
+          sudo apt-get install lua5.1
 
       - name: run test
         run: |