diff --git a/.github/workflows/preview.yaml b/.github/workflows/preview.yaml
index 0dfe49f..c6be869 100644
--- a/.github/workflows/preview.yaml
+++ b/.github/workflows/preview.yaml
@@ -20,6 +20,11 @@ jobs:
           hugo-version: 'latest'
           extended: true
 
+      - name: Setup Go
+        uses: actions/setup-go@v4.0.0
+        with:
+          go-version: '^1.21'
+
       - name: Install Vercel CLI
         run: npm install --global vercel@latest
 
diff --git a/.github/workflows/production.yaml b/.github/workflows/production.yaml
index 8b1da42..a48409b 100644
--- a/.github/workflows/production.yaml
+++ b/.github/workflows/production.yaml
@@ -19,6 +19,11 @@ jobs:
           hugo-version: 'latest'
           extended: true
 
+      - name: Setup Go
+        uses: actions/setup-go@v4.0.0
+        with:
+          go-version: '^1.21'
+
       - name: Install Vercel CLI
         run: npm install --global vercel@latest
 
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..09dee87
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module github.com/yukuro/hugo-theme-shell
+
+go 1.21