build: modernize Go usage

This commit modernizes Go usage. This was done with:

go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix -test ./...

Then files needed to be `go fmt`ed and a few comments needed to be
restored.

The modernizations include replacing

- if/else conditional assignment by a call to the built-in min or max functions added in go1.21
- sort.Slice(x, func(i, j int) bool) { return s[i] < s[j] } by a call to slices.Sort(s), added in go1.21
- interface{} by the 'any' type added in go1.18
- append([]T(nil), s...) by slices.Clone(s) or slices.Concat(s), added in go1.21
- loop around an m[k]=v map update by a call to one of the Collect, Copy, Clone, or Insert functions from the maps package, added in go1.21
- []byte(fmt.Sprintf...) by fmt.Appendf(nil, ...), added in go1.19
- append(s[:i], s[i+1]...) by slices.Delete(s, i, i+1), added in go1.21
- a 3-clause for i := 0; i < n; i++ {} loop by for i := range n {}, added in go1.22

cmd/serve/s3/backend.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"encoding/hex"
 	"io"
+	"maps"
 	"os"
 	"path"
 	"strings"
@@ -144,9 +145,7 @@ func (b *s3Backend) HeadObject(ctx context.Context, bucketName, objectName strin
 
 	if val, ok := b.meta.Load(fp); ok {
 		metaMap := val.(map[string]string)
-		for k, v := range metaMap {
-			meta[k] = v
-		}
+		maps.Copy(meta, metaMap)
 	}
 
 	return &gofakes3.Object{
@@ -221,9 +220,7 @@ func (b *s3Backend) GetObject(ctx context.Context, bucketName, objectName string
 
 	if val, ok := b.meta.Load(fp); ok {
 		metaMap := val.(map[string]string)
-		for k, v := range metaMap {
-			meta[k] = v
-		}
+		maps.Copy(meta, metaMap)
 	}
 
 	return &gofakes3.Object{

cmd/serve/s3/logger.go

@@ -11,7 +11,7 @@ import (
 type logger struct{}
 
 // print log message
-func (l logger) Print(level gofakes3.LogLevel, v ...interface{}) {
+func (l logger) Print(level gofakes3.LogLevel, v ...any) {
 	var s string
 	if len(v) == 0 {
 		s = ""

cmd/serve/s3/s3_test.go

@@ -11,19 +11,19 @@ import (
 	"net/url"
 	"path"
 	"path/filepath"
+	"slices"
 	"testing"
 	"time"
 
 	"github.com/minio/minio-go/v7"
 	"github.com/minio/minio-go/v7/pkg/credentials"
-	"github.com/rclone/rclone/fs/object"
-
 	_ "github.com/rclone/rclone/backend/local"
 	"github.com/rclone/rclone/cmd/serve/proxy/proxyflags"
 	"github.com/rclone/rclone/cmd/serve/servetest"
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/config/configmap"
 	"github.com/rclone/rclone/fs/hash"
+	"github.com/rclone/rclone/fs/object"
 	"github.com/rclone/rclone/fstest"
 	httplib "github.com/rclone/rclone/lib/http"
 	"github.com/rclone/rclone/lib/random"
@@ -226,13 +226,7 @@ func testListBuckets(t *testing.T, cases []TestCase, useProxy bool) {
 
 				for _, tt := range tt.files {
 					file := path.Join(tt.path, tt.filename)
-					found := false
-					for _, fname := range objects {
-						if file == fname {
-							found = true
-							break
-						}
-					}
+					found := slices.Contains(objects, file)
 					require.Equal(t, true, found, "Object not found: "+file)
 				}
 			}

cmd/serve/s3/server.go

@@ -122,7 +122,7 @@ func (w *Server) getVFS(ctx context.Context) (VFS *vfs.VFS, err error) {
 }
 
 // auth does proxy authorization
-func (w *Server) auth(accessKeyID string) (value interface{}, err error) {
+func (w *Server) auth(accessKeyID string) (value any, err error) {
 	VFS, _, err := w.proxy.Call(stringToMd5Hash(accessKeyID), accessKeyID, false)
 	if err != nil {
 		return nil, err

cmd/serve/s3/utils.go

@@ -36,7 +36,7 @@ func getDirEntries(prefix string, VFS *vfs.VFS) (vfs.Nodes, error) {
 	return dirEntries, nil
 }
 
-func getFileHashByte(node interface{}) []byte {
+func getFileHashByte(node any) []byte {
 	b, err := hex.DecodeString(getFileHash(node))
 	if err != nil {
 		return nil
@@ -44,7 +44,7 @@ func getFileHashByte(node interface{}) []byte {
 	return b
 }
 
-func getFileHash(node interface{}) string {
+func getFileHash(node any) string {
 	var o fs.Object
 
 	switch b := node.(type) {