gh: add action to assert dns config change

.github/workflows/dns.yml

@@ -0,0 +1,37 @@
+# Copyright 2021 The forwarder Authors. All rights reserved.
+# Use of this source code is governed by a MIT
+# license that can be found in the LICENSE file.
+
+---
+# Forwarder hacks the net package to support overriding internal DNS config.
+# This action checks the net package dns code for changes.
+name: dns
+
+on:
+  pull_request:
+    branches: [main]
+
+jobs:
+  assert:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Set version env variables
+        run: |
+          cat .version >> $GITHUB_ENV
+
+      - name: Setup Go
+        uses: actions/setup-go@v3
+        with:
+          go-version: "${{env.GO_VERSION}}"
+
+      - name: Check Hash
+        run: |
+          go env
+          echo ${GOROOT}
+          echo ${{env.GOROOT}}
+          echo ${{GOROOT}}
+
+