do not use ioutil anymore

fs.go

@@ -9,7 +9,6 @@ import (
 	"go/parser"
 	"go/token"
 	"io/fs"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -100,7 +99,7 @@ var (
 )
 
 func isGeneratedFile(filename string) (bool, error) {
-	content, err := ioutil.ReadFile(filename)
+	content, err := os.ReadFile(filename)
 	if err != nil {
 		return false, fmt.Errorf("failed to read file: %v", err)
 	}

main.go

@@ -6,7 +6,6 @@ package main
 import (
 	"flag"
 	"fmt"
-	"io/ioutil"
 	"log"
 	"os"
 	"path/filepath"
@@ -132,7 +131,7 @@ func main() {
 				}
 
 				if !dryRun {
-					if err := ioutil.WriteFile(filename, formattedOutput, 0644); err != nil {
+					if err := os.WriteFile(filename, formattedOutput, 0644); err != nil {
 						log.Fatalf("Failed to write fixed result to file %q: %v", filename, err)
 					}
 				}

pkg/gimps/gimps.go

@@ -11,7 +11,7 @@ import (
 	"go/parser"
 	"go/printer"
 	"go/token"
-	"io/ioutil"
+	"os"
 	"sort"
 	"strings"
 )
@@ -51,7 +51,7 @@ func (p *importPosition) IsInRange(comment *ast.CommentGroup) bool {
 func Execute(config *Config, filePath string, aliaser *Aliaser) ([]byte, bool, error) {
 	setDefaults(config)
 
-	originalContent, err := ioutil.ReadFile(filePath)
+	originalContent, err := os.ReadFile(filePath)
 	if err != nil {
 		return nil, false, err
 	}

pkg/gimps/gimps_test.go

@@ -4,7 +4,6 @@
 package gimps
 
 import (
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"testing"
@@ -56,7 +55,7 @@ func TestExecute(t *testing.T) {
 			}
 
 			expectedFile := filepath.Join(testcase, "main.go.expected")
-			expected, err := ioutil.ReadFile(expectedFile)
+			expected, err := os.ReadFile(expectedFile)
 			require.Nil(t, err)
 			assert.Equal(t, string(expected), string(output))
 		})