Pin GitHub action versions (#332)

Author: neild

.github/workflows/test.yml

@@ -9,11 +9,11 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
     - name: Install Go
-      uses: actions/setup-go@v2
+      uses: actions/setup-go@bfdd3570ce990073878bf10f6b2d79082de49492 # v2.2.0
       with:
         go-version: ${{ matrix.go-version }}
     - name: Checkout code
-      uses: actions/checkout@v2
+      uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2.7.0
     - name: Test
       run: go test -v -race ./...
     - name: Format