fix: upgrade golangci-lint to v2 for Go 1.25 compatibility

- Migrate .golangci.yml to v2 format (version: "2")
- Update CI action to golangci-lint-action@v9 with v2.10.1
- Remove gosimple (merged into staticcheck in v2)
- Fix unchecked r.Body.Close() errors

Author: gumeniukcom

.github/workflows/ci.yml

@@ -37,6 +37,6 @@ jobs:
           go-version: '1.25'
 
       - name: golangci-lint
-        uses: golangci/golangci-lint-action@v6
+        uses: golangci/golangci-lint-action@v9
         with:
-          version: latest
+          version: v2.10.1

.golangci.yml

@@ -1,32 +1,35 @@
+version: "2"
+
 linters:
+  default: standard
   enable:
     - errcheck
     - govet
     - staticcheck
     - unused
-    - gosimple
     - ineffassign
     - misspell
-    - gofmt
-    - goimports
     - unconvert
     - unparam
     - gocritic
     - revive
 
-linters-settings:
-  revive:
-    rules:
-      - name: exported
-        severity: warning
-  misspell:
-    locale: US
-  goimports:
-    local-prefixes: github.com/gumeniukcom/golang-jsonrpc2
+  settings:
+    revive:
+      rules:
+        - name: exported
+          severity: warning
+    misspell:
+      locale: US
+
+formatters:
+  enable:
+    - gofmt
+    - goimports
+  settings:
+    goimports:
+      local-prefixes: github.com/gumeniukcom/golang-jsonrpc2
 
 issues:
-  exclude-dirs:
-    - vendor
-  exclude-generated: strict
   max-issues-per-linter: 50
   max-same-issues: 5

example/main.go

@@ -22,7 +22,7 @@ func main() {
 		if err != nil {
 			panic(err)
 		}
-		defer r.Body.Close()
+		defer func() { _ = r.Body.Close() }()
 
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusOK)

main_test.go

@@ -52,7 +52,7 @@ func TestAll(t *testing.T) {
 		if err != nil {
 			panic(err)
 		}
-		defer r.Body.Close()
+		defer func() { _ = r.Body.Close() }()
 
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusOK)
@@ -116,7 +116,7 @@ func TestCallPanic(t *testing.T) {
 		if err != nil {
 			panic(err)
 		}
-		defer r.Body.Close()
+		defer func() { _ = r.Body.Close() }()
 
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusOK)