actions: use go-version-file: .go-version

 see actions/setup-go#295

Author: v1v

.github/workflows/Periodic-CI.yml

@@ -74,15 +74,12 @@ jobs:
     timeout-minutes: 15
     steps:
       - name: Check out the repo
-        uses: actions/checkout@v2
-
-      - name: Fetch Go version from .go-version
-        run: echo "GO_VERSION=$(cat .go-version)" >> $GITHUB_ENV
+        uses: actions/checkout@v3
 
       - name: Set up Go
-        uses: actions/setup-go@v2
+        uses: actions/setup-go@v3
         with:
-          go-version: ${{ env.GO_VERSION }}
+          go-version-file: .go-version
 
       - name: Fetch OPA version
         run: echo "OPA_VERSION=$(go list -m -f {{.Version}} github.com/open-policy-agent/opa | sed 's/v//')" >> $GITHUB_ENV

.github/workflows/unit-test.yml

@@ -109,12 +109,10 @@ jobs:
     timeout-minutes: 15
     steps:
       - name: Check out the repo
-        uses: actions/checkout@v2
-      - name: Fetch Go version from .go-version
-        run: echo "GO_VERSION=$(cat .go-version)" >> $GITHUB_ENV
+        uses: actions/checkout@v3
       - uses: actions/setup-go@v3
         with:
-          go-version: ${{ env.GO_VERSION }}
+          go-version-file: .go-version
       - name: Check out the repo
         uses: actions/checkout@v3
         with: