Create expensive.yml

Run -count=1000 occasionally.

.github/workflows/expensive.yml

@@ -0,0 +1,16 @@
+name: Run
+on:
+  schedule:
+    - cron: '0 16 * * 1'
+  workflow_dispatch: {}
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+      - name: Test
+        run: go test -count=1000 -shuffle=on -failfast ./...