chore: add checkout phase

Author: apuerta

.github/workflows/ci.yml

@@ -9,6 +9,9 @@ jobs:
   main:
     runs-on: ubuntu-latest
     steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
       - name: Set up Go
         uses: actions/setup-go@v4
         with: