Update GitHub workflow

GitHub plans to remove the old versions of the steps this year.

Author: rillig

.github/workflows/go.yml

@@ -13,15 +13,15 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
 
-    - name: Set up Go
-      uses: actions/setup-go@v4
-      with:
-        go-version: '1.20'
+      - name: Set up Go
+        uses: actions/setup-go@v6
+        with:
+          go-version: '1.20'
 
-    - name: Build and test
-      run: sh ./test.sh
+      - name: Build and test
+        run: sh ./test.sh
 
-    - name: Upload coverage data
-      run: bash <(curl -s https://codecov.io/bash)
+      - name: Upload coverage data
+        run: bash <(curl -s https://codecov.io/bash)