add auto-update workflow

.github/workflows/autoupdate.yml

@@ -0,0 +1,26 @@
+name: auto-update
+on:
+  schedule:
+    # runs every two weeks
+    - cron: '0 8 1 * *'
+  workflow_dispatch:
+
+jobs:
+  auto-update:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout the head commit of the branch
+      uses: actions/checkout@v2
+      with:
+        persist-credentials: false
+
+    - name: Go setup
+      uses: actions/setup-go@v2
+
+    - name: Run auto dependency update
+      uses: psycofdj/dependencies-autoupdate@v1
+      with:
+        token: ${{ secrets.GITHUB_TOKEN }}
+        update-command: go get -u -t ./... && go mod tidy && go mod vendor && go build ./... && go test ./...
+        base-branch-name: master