chore(lint): update golangci config and fix test cleanup

Update .golangci.yml to use config version 2 and re-enable tenv and gofumpt linters
Ensure cli checkstyle test checks errors from temporary file Close()
Update golangci-lint action

Author: ryancurrah

.github/workflows/go.yml

@@ -33,7 +33,7 @@ jobs:
       run: make build
 
     - name: golangci-lint
-      uses: golangci/golangci-lint-action@v6
+      uses: golangci/golangci-lint-action@v9
       with:
         version: latest
 

.golangci.yml

@@ -1,8 +1,8 @@
-# See https://golangci-lint.run/usage/configuration/
+version: 2
+
 linters:
   enable-all: true
   disable:
-    - tenv
     - lll
     - gomodguard
     - gochecknoglobals
@@ -13,7 +13,6 @@ linters:
     - forbidigo
     - funlen
     - nlreturn
-    - gofumpt
     - nonamedreturns
     - cyclop
     - err113

internal/cli/cli_test.go

@@ -33,7 +33,10 @@ func TestCmdRun(t *testing.T) {
 func TestWriteCheckstyle(t *testing.T) {
 	outFile, err := os.CreateTemp(t.TempDir(), "checkstyle-*.xml")
 	require.NoError(t, err)
-	defer outFile.Close()
+	defer func() {
+		err := outFile.Close()
+		require.NoError(t, err)
+	}()
 
 	issues := []gomodguard.Issue{
 		{