Add missing checkout step

.github/workflows/coverage.yml

@@ -3,18 +3,22 @@ on: [push, pull_request]
 
 jobs:
   coverage:
+    name: Report Coverage
     runs-on: ubuntu-latest
     steps:
       - name: Install Go
         uses: actions/setup-go@v2
         with:
           go-version: "1.17.6"
 
+      - name: Check out code
+        uses: actions/checkout@v2
+
       - name: Install deps
         run: |
           go mod download
 
-      - name: Run tests
+      - name: Run tests with coverage output
         run: |
           go test -race -covermode atomic -coverprofile=covprofile ./...