Use actions/checkout@v2

Author: jvalkeal

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
         os: [ubuntu-latest]
 
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
     - name: Cache maven repository
       uses: actions/cache@v1
       with: