dev: use setup-go@v2 and mod cache

.github/workflows/pr.yml

@@ -18,7 +18,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Install Go
-        uses: actions/setup-go@v1
+        uses: actions/setup-go@v2
         with:
           go-version: ${{ matrix.golang }}
       - name: Run tests on Windows
@@ -37,9 +37,15 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Install Go
-        uses: actions/setup-go@v1
+        uses: actions/setup-go@v2
         with:
           go-version: ${{ matrix.golang }}
+      - uses: actions/cache@v1
+        with:
+          path: ~/go/pkg/mod
+          key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+          restore-keys: |
+            ${{ runner.os }}-go-
       - name: Run tests on Unix-like operating systems
         run: make test
   check_generated:
@@ -49,7 +55,7 @@ jobs:
       - name: Unshallow
         run: git fetch --prune --unshallow
       - name: Install Go
-        uses: actions/setup-go@v1
+        uses: actions/setup-go@v2
         with:
           go-version: 1.14
       - name: Check if README.md is up to date