diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a1143c9..c51bddc 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -22,7 +22,7 @@ jobs:
       - name: Set up latest Go 1.x version
         uses: actions/setup-go@v2
         with:
-          go-version: '1.17'
+          go-version: '1.21'
       - name: Get dependencies
         run: |
           go mod tidy
@@ -36,7 +36,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: ['1.13', '1.14', '1.15', '1.16', '1.17']
+        go-version: ['1.13', '1.14', '1.15', '1.16', '1.17', '1.18', '1.19', '1.20', '1.21']
     steps:
       - name: Set up Go ${{ matrix.go-version }}
         uses: actions/setup-go@v2
diff --git a/examples/webhooks/main.go b/examples/webhooks/main.go
index fdee9b6..ec4a40a 100644
--- a/examples/webhooks/main.go
+++ b/examples/webhooks/main.go
@@ -85,12 +85,12 @@ func HandleTemplateDelete(rw http.ResponseWriter, tpl v1.TemplateDeleteWebhookDa
 	serveJSON(rw, http.StatusOK, H{})
 }
 
-func readJSON(req *http.Request, out any) error {
+func readJSON(req *http.Request, out interface{}) error {
 	defer func() { _ = req.Body.Close() }()
 	return json.NewDecoder(req.Body).Decode(out)
 }
 
-func serveJSON(rw http.ResponseWriter, st int, data any) {
+func serveJSON(rw http.ResponseWriter, st int, data interface{}) {
 	resp, _ := json.Marshal(data)
 	rw.Header().Set("Content-Type", "application/json; charset=utf-8")
 	rw.WriteHeader(st)