cache during update

Author: thepwagner

.github/workflows/update.yaml

@@ -13,6 +13,12 @@ jobs:
       - uses: actions/checkout@v2
         with:
           token: ${{ secrets.MY_GITHUB_PAT }}
+      - uses: actions/cache@v2
+        with:
+          path: ~/go/pkg/mod
+          key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+          restore-keys: |
+            ${{ runner.os }}-go-
       - uses: actions/setup-go@v2
         with:
           go-version: '1.15.6'