Add caching to CI jobs (#13712)

- Seems to be improving times for shorter jobs at least.

- Remove Go 1.16.x tests for IAM and replication

.github/workflows/replication.yaml

@@ -18,13 +18,21 @@ jobs:
 
     strategy:
       matrix:
-        go-version: [1.16.x, 1.17.x]
+        go-version: [1.17.x]
 
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-go@v2
         with:
           go-version: ${{ matrix.go-version }}
+      - uses: actions/cache@v2
+        with:
+          path: |
+            ~/.cache/go-build
+            ~/go/pkg/mod
+          key: ${{ runner.os }}-${{ matrix.go-version }}-go-${{ hashFiles('**/go.sum') }}
+          restore-keys: |
+            ${{ runner.os }}-${{ matrix.go-version }}-go-
       - name: Test Replication
         run: |
           sudo sysctl net.ipv6.conf.all.disable_ipv6=0