GitHub Actions: update to latest versions of actions

.github/workflows/push.yml

@@ -9,21 +9,18 @@ jobs:
     name: CI
     runs-on: ubuntu-latest
     steps:
+    - uses: actions/checkout@v4
 
-    - name: Set up Go 1.x
-      uses: actions/setup-go@v2
+    - name: Set up latest stable Go
+      uses: actions/setup-go@v5
       with:
-        # Run on the latest minor release of Go 1.19:
-        go-version: ^1.19
-      id: go
-
-    - name: Check out code into the Go module directory
-      uses: actions/checkout@v2
+        go-version: 'stable'
 
     - name: Ensure all files were formatted as per gofmt
       run: |
         [ "$(gofmt -l $(find . -name '*.go') 2>&1)" = "" ]
 
-    - name: Build packages
+    - name: Build and test
       run: |
-        go install -v ./...
+        go install ./...
+        go test -v ./...