ci: update test/lint pipeline

Also correct some linter issues.

.github/workflows/lint.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
 
     env:
-      GO_VERSION: 1.16
+      GO_VERSION: 1.21
 
     steps:
     - name: Set up Go ${{ env.GO_VERSION }}
@@ -40,4 +40,4 @@ jobs:
     - name: golangci-lint
       uses: golangci/golangci-lint-action@v2
       with:
-        version: v1.37
+        version: v1.52

.github/workflows/test.yml

@@ -8,7 +8,7 @@ jobs:
 
     strategy:
       matrix:
-        go-version: [1.13, 1.14, 1.15, 1.16, 1.x]
+        go-version: [1.20, 1.21, 1.x]
 
     steps:
     - name: Set up Go ${{ matrix.go-version }}

uci.go

@@ -3,7 +3,6 @@ package uci
 import (
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"sync"
@@ -118,7 +117,7 @@ func (t *tree) LoadConfig(name string, forceReload bool) error {
 // loadConfig actually reads a config file. Its call must be guarded by
 // locking the tree's mutex.
 func (t *tree) loadConfig(name string) error {
-	body, err := ioutil.ReadFile(filepath.Join(t.dir, name))
+	body, err := os.ReadFile(filepath.Join(t.dir, name))
 	if err != nil {
 		return fmt.Errorf("reading config file failed: %w", err)
 	}
@@ -359,7 +358,7 @@ func (t *tree) saveConfig(c *config) error {
 		return err
 	}
 
-	if err = f.Chmod(0644); err != nil {
+	if err = f.Chmod(0o644); err != nil {
 		f.Close()
 		_ = f.Remove()
 		return fmt.Errorf("save: failed to set permissions: %w", err)
@@ -391,7 +390,7 @@ type tmpFile interface {
 
 // newTmpFile purely exists to be replaced in tests.
 var newTmpFile = func(dir, pattern string) (tmpFile, error) {
-	f, err := ioutil.TempFile(dir, pattern)
+	f, err := os.CreateTemp(dir, pattern)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create temp file: %w", err)
 	}