chore: pin GitHub Actions to commit SHAs (#236)

Author: bolchowka

.github/workflows/unittests.yml

@@ -12,10 +12,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Set up Go
-        uses: actions/setup-go@v2
+        uses: actions/setup-go@bfdd3570ce990073878bf10f6b2d79082de49492 # v2.2.0
         with:
           go-version: ${{ env.GO_VERSION }}
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2.7.0
       - name: Run Unit Tests
         run: go test -v ./...