diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 64215b7..75088ce 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -22,7 +22,7 @@ jobs:
           fetch-depth: 0
       - uses: actions/setup-node@v3
         with:
-          node-version: 18.x
+          node-version: 20.x
           registry-url: 'https://registry.npmjs.org'
       - run: npm version
       - run: npm install
diff --git a/.gitignore b/.gitignore
index e833970..6ef090c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,4 +16,4 @@ _archive
 .npmrc*
 lib
 docs
-_sandbox
+# _sandbox
diff --git a/_sandbox/using-class.ts b/_sandbox/using-class.ts
new file mode 100755
index 0000000..a2edfb2
--- /dev/null
+++ b/_sandbox/using-class.ts
@@ -0,0 +1,22 @@
+#!/usr/bin/env bun
+
+/* eslint-disable no-console */
+
+class TempFile implements Disposable {
+  constructor(path: string) {
+    console.log('2 constructor')
+  }
+
+  [Symbol.dispose]() {
+    console.log('4 dispose')
+  }
+}
+
+function fn() {
+  using f = new TempFile('abc')
+  console.log('3 fn return')
+}
+
+console.log('1 fn before')
+fn()
+console.log('5 fn after')
diff --git a/_sandbox/using.ts b/_sandbox/using.ts
new file mode 100755
index 0000000..2852303
--- /dev/null
+++ b/_sandbox/using.ts
@@ -0,0 +1,32 @@
+#!/usr/bin/env bun
+
+/* eslint-disable no-console */
+
+// https://www.typescriptlang.org/docs/handbook/release-notes/typescript-5-2.html
+
+// try {
+//   // @ts-expect-error just a polyfill
+//   Symbol.dispose ??= Symbol("Symbol.dispose") 
+//   // @ts-expect-error just a polyfill
+//   Symbol.asyncDispose ??= Symbol("Symbol.asyncDispose")
+// } finally { }
+
+function useTempFile(path: string) {
+  console.log('2 constructor')
+  return {
+    path,
+    [Symbol.dispose]() {
+      console.log('4 dispose')
+    }
+  }
+}
+
+function fn() {
+  using f = useTempFile('abc')
+  console.log('x using return:', f)
+  console.log('3 fn return')
+}
+
+console.log('1 fn before')
+fn()
+console.log('5 fn after')
diff --git a/package.json b/package.json
index 41acf5e..23a5710 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "zeed",
   "type": "module",
-  "version": "0.20.8",
+  "version": "0.20.9",
   "description": "🌱 Simple foundation library",
   "author": {
     "name": "Dirk Holtwick",