Update actions/checkout action to v4

.github/workflows/mdbook.yaml

@@ -9,7 +9,7 @@ jobs:
     name: Build book
     runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
     - run: make book
     - uses: actions/upload-artifact@v3
       with:
@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-20.04
     needs: build
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       with:
         ref: gh-pages
     - uses: actions/download-artifact@v3

.github/workflows/mdbook_close_preview.yaml

@@ -12,7 +12,7 @@ jobs:
       shell: bash
       run: echo "::set-output name=branch::$(REF=${GITHUB_HEAD_REF:-$GITHUB_REF} && echo ${REF#refs/heads/} | sed 's/\//-/g')"
       id: extract_branch
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       with:
         ref: gh-pages
     - run: rm -rf _preview/${{ steps.extract_branch.outputs.branch }}

.github/workflows/mdbook_preview.yaml

@@ -12,7 +12,7 @@ jobs:
       shell: bash
       run: echo "::set-output name=branch::$(REF=${GITHUB_HEAD_REF:-$GITHUB_REF} && echo ${REF#refs/heads/} | sed 's/\//-/g')"
       id: extract_branch
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
     - run: make book
     - uses: actions/upload-artifact@v3
       with:
@@ -24,7 +24,7 @@ jobs:
     runs-on: ubuntu-20.04
     needs: build
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       with:
         ref: gh-pages
     - run: rm -rf _preview/${{ needs.build.outputs.branch }}

.github/workflows/release.yaml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
         with:
           fetch-depth: 1
       - name: Setup Go

.github/workflows/test_and_build.yaml

@@ -31,7 +31,7 @@ jobs:
         with:
           go-version: ${{ env.go-version }}
       - name: checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - name: build
         run: make build
   test:
@@ -43,7 +43,7 @@ jobs:
         with:
           go-version: ${{ env.go-version }}
       - name: checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - name: Ensure go.mod is already tidied
         run: go mod tidy && git diff -s --exit-code go.sum
       - name: test