Don't attempt to use the secret if it does not exist.

Fixes #3326

PiperOrigin-RevId: 323589669

.github/workflows/go.yml

@@ -11,7 +11,13 @@ jobs:
   generate:
     runs-on: ubuntu-latest
     steps:
-    - run: |
+    - id: setup
+      run: |
+        if ! [[ -z "${{ secrets.GO_TOKEN }}" ]]; then
+           echo ::set-output has_token=true
+        else
+           echo ::set-output has_token=false
+        fi
         jq -nc '{"state": "pending", "context": "go tests"}' | \
         curl -sL -X POST -d @- \
             -H "Content-Type: application/json" \
@@ -19,12 +25,12 @@ jobs:
             "${{ github.event.pull_request.statuses_url }}"
       if: github.event_name == 'pull_request'
     - uses: actions/checkout@v2
-      if: github.event_name == 'push'
+      if: github.event_name == 'push' && steps.setup.outputs.has_token == 'true'
       with:
         fetch-depth: 0
         token: '${{ secrets.GO_TOKEN }}'
     - uses: actions/checkout@v2
-      if: github.event_name == 'pull_request'
+      if: github.event_name == 'pull_request' || steps.setup.outputs.has_token != 'true'
       with:
         fetch-depth: 0
     - uses: actions/setup-go@v2