increment cache key version

Author: Dean Karn

.github/workflows/go.yml

@@ -17,9 +17,9 @@ jobs:
         uses: actions/cache@v1
         with:
           path: ~/go/pkg/mod
-          key: ${{ runner.os }}-v1-go-${{ hashFiles('**/go.sum') }}
+          key: ${{ runner.os }}-v2-go-${{ hashFiles('**/go.sum') }}
           restore-keys: |
-            ${{ runner.os }}-v1-go-
+            ${{ runner.os }}-v2-go-
 
       - name: Checkout code
         uses: actions/checkout@v2