diff --git a/.github/workflows/cache.yml b/.github/workflows/cache.yml
index f990cc5d..ead760f4 100644
--- a/.github/workflows/cache.yml
+++ b/.github/workflows/cache.yml
@@ -10,7 +10,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        go: ['1.20.x', '1.21.x']
+        go: ['1.21.x']
 
     services:
       memcached:
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 7da819b6..27d68140 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -10,7 +10,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macOS-latest, windows-latest]
-        go: ['1.20.x', '1.21.x']
+        go: ['1.21.x']
 
     steps:
 
diff --git a/context.go b/context.go
index 059cf2bd..bca6786e 100644
--- a/context.go
+++ b/context.go
@@ -6,12 +6,12 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"slices"
 	"strings"
 	"sync"
 	"time"
 
 	"github.com/issue9/mux/v7/types"
-	"github.com/issue9/sliceutil"
 	"golang.org/x/text/encoding"
 	"golang.org/x/text/language"
 	"golang.org/x/text/message"
@@ -184,7 +184,7 @@ func (b *ContextBuilder) NewContext(w http.ResponseWriter, r *http.Request, rout
 	ctx.inputCharset = inputCharset
 	ctx.languageTag = tag
 	ctx.localePrinter = b.server.Locale().NewPrinter(tag)
-	ctx.vars = map[any]any{} // TODO: go1.21 可以改为 clear(ctx.vars)
+	clear(ctx.vars)
 	ctx.logs = b.server.Logs().New(map[string]any{b.requestIDKey: id})
 
 	return ctx
@@ -300,7 +300,7 @@ func (ctx *Context) LocalePrinter() *message.Printer { return ctx.localePrinter
 func (ctx *Context) LanguageTag() language.Tag { return ctx.languageTag }
 
 func (ctx *Context) Free() {
-	sliceutil.Reverse(ctx.exits) // TODO: go1.21 改为标准库
+	slices.Reverse(ctx.exits)
 	for _, exit := range ctx.exits {
 		exit(ctx, ctx.status)
 	}
diff --git a/go.mod b/go.mod
index 6256e5f2..c1082039 100644
--- a/go.mod
+++ b/go.mod
@@ -33,4 +33,4 @@ require (
 	golang.org/x/sys v0.14.0 // indirect
 )
 
-go 1.20
+go 1.21
diff --git a/server/server.go b/server/server.go
index eb04cfef..69914b04 100644
--- a/server/server.go
+++ b/server/server.go
@@ -9,12 +9,12 @@ import (
 	"context"
 	"errors"
 	"net/http"
+	"slices"
 	"sync"
 	"time"
 
 	"github.com/issue9/config"
 	"github.com/issue9/mux/v7/group"
-	"github.com/issue9/sliceutil"
 
 	"github.com/issue9/web"
 	"github.com/issue9/web/cache"
@@ -145,7 +145,7 @@ func (srv *httpServer) Close(shutdownTimeout time.Duration) {
 	}
 
 	defer func() {
-		sliceutil.Reverse(srv.closes)  // TODO: go1.21 改为标准库
+		slices.Reverse(srv.closes)
 		for _, f := range srv.closes { // 仅在用户主动要关闭时，才关闭服务。
 			if err1 := f(); err1 != nil { // 出错不退出，继续其它操作。
 				srv.Logs().ERROR().Error(err1)