Cache Go files in CI (#31)

Closes #30

.github/workflows/ci.yml

@@ -51,6 +51,7 @@ jobs:
           allow-prereleases: true
 
       - name: Set up Go toolchain
+        id: setup-go
         uses: actions/setup-go@v5
         with:
           go-version: "1.21.x"
@@ -61,6 +62,13 @@ jobs:
         if: matrix.runs-on == 'windows-latest'
         run: choco install mingw
 
+      - name: Restore or save Hugo builder cache
+        uses: actions/cache@v3
+        with:
+          path: ./hugo_cache/
+          key: ${{ runner.os }}-hugo-${{ hashFiles('**/setup.py') }}-${{ steps.setup-go.outputs.go-version }}
+          # restore-keys: ${{ runner.os }}-hugo-${{ hashFiles('**/setup.py') }}
+
       - name: Install Python dependencies
         run: python -m pip install build virtualenv nox