diff --git a/.github/workflows/gin.yml b/.github/workflows/gin.yml
index 2e434341..4a9dbc93 100644
--- a/.github/workflows/gin.yml
+++ b/.github/workflows/gin.yml
@@ -34,7 +34,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest]
-        go: ["1.18", "1.19", "1.20", "1.21", "1.22"]
+        go: ["1.20", "1.21", "1.22"]
         test-tags:
           ["", "-tags nomsgpack", '-tags "sonic avx"', "-tags go_json", "-race"]
         include:
diff --git a/context_1.18_test.go b/context_1.18_test.go
deleted file mode 100644
index 6118beaa..00000000
--- a/context_1.18_test.go
+++ /dev/null
@@ -1,37 +0,0 @@
-// Copyright 2021 Gin Core Team. All rights reserved.
-// Use of this source code is governed by a MIT style
-// license that can be found in the LICENSE file.
-
-//go:build !go1.19
-
-package gin
-
-import (
-	"bytes"
-	"mime/multipart"
-	"net/http"
-	"net/http/httptest"
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-)
-
-func TestContextFormFileFailed18(t *testing.T) {
-	buf := new(bytes.Buffer)
-	mw := multipart.NewWriter(buf)
-	defer func(mw *multipart.Writer) {
-		err := mw.Close()
-		if err != nil {
-			assert.Error(t, err)
-		}
-	}(mw)
-	c, _ := CreateTestContext(httptest.NewRecorder())
-	c.Request, _ = http.NewRequest("POST", "/", nil)
-	c.Request.Header.Set("Content-Type", mw.FormDataContentType())
-	c.engine.MaxMultipartMemory = 8 << 20
-	assert.Panics(t, func() {
-		f, err := c.FormFile("file")
-		assert.Error(t, err)
-		assert.Nil(t, f)
-	})
-}
diff --git a/context_1.19_test.go b/context_1.19_test.go
deleted file mode 100644
index dd75325b..00000000
--- a/context_1.19_test.go
+++ /dev/null
@@ -1,30 +0,0 @@
-// Copyright 2022 Gin Core Team. All rights reserved.
-// Use of this source code is governed by a MIT style
-// license that can be found in the LICENSE file.
-
-//go:build go1.19
-
-package gin
-
-import (
-	"bytes"
-	"mime/multipart"
-	"net/http"
-	"net/http/httptest"
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-)
-
-func TestContextFormFileFailed19(t *testing.T) {
-	buf := new(bytes.Buffer)
-	mw := multipart.NewWriter(buf)
-	mw.Close()
-	c, _ := CreateTestContext(httptest.NewRecorder())
-	c.Request, _ = http.NewRequest("POST", "/", nil)
-	c.Request.Header.Set("Content-Type", mw.FormDataContentType())
-	c.engine.MaxMultipartMemory = 8 << 20
-	f, err := c.FormFile("file")
-	assert.Error(t, err)
-	assert.Nil(t, f)
-}
diff --git a/context_test.go b/context_test.go
index e9bbae52..ae34c659 100644
--- a/context_test.go
+++ b/context_test.go
@@ -90,6 +90,19 @@ func TestContextFormFile(t *testing.T) {
 	assert.NoError(t, c.SaveUploadedFile(f, "test"))
 }
 
+func TestContextFormFileFailed(t *testing.T) {
+	buf := new(bytes.Buffer)
+	mw := multipart.NewWriter(buf)
+	mw.Close()
+	c, _ := CreateTestContext(httptest.NewRecorder())
+	c.Request, _ = http.NewRequest("POST", "/", nil)
+	c.Request.Header.Set("Content-Type", mw.FormDataContentType())
+	c.engine.MaxMultipartMemory = 8 << 20
+	f, err := c.FormFile("file")
+	assert.Error(t, err)
+	assert.Nil(t, f)
+}
+
 func TestContextMultipartForm(t *testing.T) {
 	buf := new(bytes.Buffer)
 	mw := multipart.NewWriter(buf)
diff --git a/debug.go b/debug.go
index 1761fe32..ae346e9c 100644
--- a/debug.go
+++ b/debug.go
@@ -10,6 +10,7 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
+	"sync/atomic"
 )
 
 const ginSupportMinGoVer = 18
@@ -17,7 +18,7 @@ const ginSupportMinGoVer = 18
 // IsDebugging returns true if the framework is running in debug mode.
 // Use SetMode(gin.ReleaseMode) to disable debug mode.
 func IsDebugging() bool {
-	return ginMode == debugCode
+	return atomic.LoadInt32(&ginMode) == debugCode
 }
 
 // DebugPrintRouteFunc indicates debug log output format.
@@ -77,7 +78,7 @@ func getMinVer(v string) (uint64, error) {
 
 func debugPrintWARNINGDefault() {
 	if v, e := getMinVer(runtime.Version()); e == nil && v < ginSupportMinGoVer {
-		debugPrint(`[WARNING] Now Gin requires Go 1.18+.
+		debugPrint(`[WARNING] Now Gin requires Go 1.20+.
 
 `)
 	}
diff --git a/debug_test.go b/debug_test.go
index 2d5e9a56..e3909729 100644
--- a/debug_test.go
+++ b/debug_test.go
@@ -104,7 +104,7 @@ func TestDebugPrintWARNINGDefault(t *testing.T) {
 	})
 	m, e := getMinVer(runtime.Version())
 	if e == nil && m < ginSupportMinGoVer {
-		assert.Equal(t, "[GIN-debug] [WARNING] Now Gin requires Go 1.18+.\n\n[GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.\n\n", re)
+		assert.Equal(t, "[GIN-debug] [WARNING] Now Gin requires Go 1.20+.\n\n[GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.\n\n", re)
 	} else {
 		assert.Equal(t, "[GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.\n\n", re)
 	}
diff --git a/fs.go b/fs.go
index f17d7434..51c3db86 100644
--- a/fs.go
+++ b/fs.go
@@ -9,37 +9,43 @@ import (
 	"os"
 )
 
-type onlyFilesFS struct {
-	fs http.FileSystem
+// OnlyFilesFS implements an http.FileSystem without `Readdir` functionality.
+type OnlyFilesFS struct {
+	FileSystem http.FileSystem
 }
 
-type neuteredReaddirFile struct {
-	http.File
-}
+// Open passes `Open` to the upstream implementation without `Readdir` functionality.
+func (o OnlyFilesFS) Open(name string) (http.File, error) {
+	f, err := o.FileSystem.Open(name)
 
-// Dir returns a http.FileSystem that can be used by http.FileServer(). It is used internally
-// in router.Static().
-// if listDirectory == true, then it works the same as http.Dir() otherwise it returns
-// a filesystem that prevents http.FileServer() to list the directory files.
-func Dir(root string, listDirectory bool) http.FileSystem {
-	fs := http.Dir(root)
-	if listDirectory {
-		return fs
-	}
-	return &onlyFilesFS{fs}
-}
-
-// Open conforms to http.Filesystem.
-func (fs onlyFilesFS) Open(name string) (http.File, error) {
-	f, err := fs.fs.Open(name)
 	if err != nil {
 		return nil, err
 	}
-	return neuteredReaddirFile{f}, nil
+
+	return neutralizedReaddirFile{f}, nil
 }
 
-// Readdir overrides the http.File default implementation.
-func (f neuteredReaddirFile) Readdir(_ int) ([]os.FileInfo, error) {
+// neutralizedReaddirFile wraps http.File with a specific implementation of `Readdir`.
+type neutralizedReaddirFile struct {
+	http.File
+}
+
+// Readdir overrides the http.File default implementation and always returns nil.
+func (n neutralizedReaddirFile) Readdir(_ int) ([]os.FileInfo, error) {
 	// this disables directory listing
 	return nil, nil
 }
+
+// Dir returns an http.FileSystem that can be used by http.FileServer().
+// It is used internally in router.Static().
+// if listDirectory == true, then it works the same as http.Dir(),
+// otherwise it returns a filesystem that prevents http.FileServer() to list the directory files.
+func Dir(root string, listDirectory bool) http.FileSystem {
+	fs := http.Dir(root)
+
+	if listDirectory {
+		return fs
+	}
+
+	return &OnlyFilesFS{FileSystem: fs}
+}
diff --git a/fs_test.go b/fs_test.go
new file mode 100644
index 00000000..a1690cd9
--- /dev/null
+++ b/fs_test.go
@@ -0,0 +1,71 @@
+package gin
+
+import (
+	"errors"
+	"net/http"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type mockFileSystem struct {
+	open func(name string) (http.File, error)
+}
+
+func (m *mockFileSystem) Open(name string) (http.File, error) {
+	return m.open(name)
+}
+
+func TestOnlyFilesFS_Open(t *testing.T) {
+	var testFile *os.File
+	mockFS := &mockFileSystem{
+		open: func(name string) (http.File, error) {
+			return testFile, nil
+		},
+	}
+	fs := &OnlyFilesFS{FileSystem: mockFS}
+
+	file, err := fs.Open("foo")
+
+	assert.NoError(t, err)
+	assert.Equal(t, testFile, file.(neutralizedReaddirFile).File)
+}
+
+func TestOnlyFilesFS_Open_err(t *testing.T) {
+	testError := errors.New("mock")
+	mockFS := &mockFileSystem{
+		open: func(_ string) (http.File, error) {
+			return nil, testError
+		},
+	}
+	fs := &OnlyFilesFS{FileSystem: mockFS}
+
+	file, err := fs.Open("foo")
+
+	assert.ErrorIs(t, err, testError)
+	assert.Nil(t, file)
+}
+
+func Test_neuteredReaddirFile_Readdir(t *testing.T) {
+	n := neutralizedReaddirFile{}
+
+	res, err := n.Readdir(0)
+
+	assert.NoError(t, err)
+	assert.Nil(t, res)
+}
+
+func TestDir_listDirectory(t *testing.T) {
+	testRoot := "foo"
+	fs := Dir(testRoot, true)
+
+	assert.Equal(t, http.Dir(testRoot), fs)
+}
+
+func TestDir(t *testing.T) {
+	testRoot := "foo"
+	fs := Dir(testRoot, false)
+
+	assert.Equal(t, &OnlyFilesFS{FileSystem: http.Dir(testRoot)}, fs)
+}
diff --git a/internal/bytesconv/bytesconv_1.20.go b/internal/bytesconv/bytesconv.go
similarity index 97%
rename from internal/bytesconv/bytesconv_1.20.go
rename to internal/bytesconv/bytesconv.go
index 5b6040a6..a02c53c3 100644
--- a/internal/bytesconv/bytesconv_1.20.go
+++ b/internal/bytesconv/bytesconv.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a MIT style
 // license that can be found in the LICENSE file.
 
-//go:build go1.20
-
 package bytesconv
 
 import (
diff --git a/internal/bytesconv/bytesconv_1.19.go b/internal/bytesconv/bytesconv_1.19.go
deleted file mode 100644
index 669c9c91..00000000
--- a/internal/bytesconv/bytesconv_1.19.go
+++ /dev/null
@@ -1,26 +0,0 @@
-// Copyright 2020 Gin Core Team. All rights reserved.
-// Use of this source code is governed by a MIT style
-// license that can be found in the LICENSE file.
-
-//go:build !go1.20
-
-package bytesconv
-
-import (
-	"unsafe"
-)
-
-// StringToBytes converts string to byte slice without a memory allocation.
-func StringToBytes(s string) []byte {
-	return *(*[]byte)(unsafe.Pointer(
-		&struct {
-			string
-			Cap int
-		}{s, len(s)},
-	))
-}
-
-// BytesToString converts byte slice to string without a memory allocation.
-func BytesToString(b []byte) string {
-	return *(*string)(unsafe.Pointer(&b))
-}
diff --git a/mode.go b/mode.go
index fd26d907..13aa3be0 100644
--- a/mode.go
+++ b/mode.go
@@ -8,6 +8,7 @@ import (
 	"flag"
 	"io"
 	"os"
+	"sync/atomic"
 
 	"github.com/gin-gonic/gin/binding"
 )
@@ -43,10 +44,8 @@ var DefaultWriter io.Writer = os.Stdout
 // DefaultErrorWriter is the default io.Writer used by Gin to debug errors
 var DefaultErrorWriter io.Writer = os.Stderr
 
-var (
-	ginMode  = debugCode
-	modeName = DebugMode
-)
+var ginMode int32 = debugCode
+var modeName atomic.Value
 
 func init() {
 	mode := os.Getenv(EnvGinMode)
@@ -64,17 +63,16 @@ func SetMode(value string) {
 	}
 
 	switch value {
-	case DebugMode:
-		ginMode = debugCode
+	case DebugMode, "":
+		atomic.StoreInt32(&ginMode, debugCode)
 	case ReleaseMode:
-		ginMode = releaseCode
+		atomic.StoreInt32(&ginMode, releaseCode)
 	case TestMode:
-		ginMode = testCode
+		atomic.StoreInt32(&ginMode, testCode)
 	default:
 		panic("gin mode unknown: " + value + " (available mode: debug release test)")
 	}
-
-	modeName = value
+	modeName.Store(value)
 }
 
 // DisableBindValidation closes the default validator.
@@ -96,5 +94,5 @@ func EnableJsonDecoderDisallowUnknownFields() {
 
 // Mode returns current gin mode.
 func Mode() string {
-	return modeName
+	return modeName.Load().(string)
 }
diff --git a/mode_test.go b/mode_test.go
index 2407f463..be03a9d0 100644
--- a/mode_test.go
+++ b/mode_test.go
@@ -5,8 +5,8 @@
 package gin
 
 import (
-	"flag"
 	"os"
+	"sync/atomic"
 	"testing"
 
 	"github.com/gin-gonic/gin/binding"
@@ -18,31 +18,24 @@ func init() {
 }
 
 func TestSetMode(t *testing.T) {
-	assert.Equal(t, testCode, ginMode)
+	assert.Equal(t, int32(testCode), atomic.LoadInt32(&ginMode))
 	assert.Equal(t, TestMode, Mode())
 	os.Unsetenv(EnvGinMode)
 
 	SetMode("")
-	assert.Equal(t, testCode, ginMode)
+	assert.Equal(t, int32(testCode), atomic.LoadInt32(&ginMode))
 	assert.Equal(t, TestMode, Mode())
 
-	tmp := flag.CommandLine
-	flag.CommandLine = flag.NewFlagSet("", flag.ContinueOnError)
-	SetMode("")
-	assert.Equal(t, debugCode, ginMode)
-	assert.Equal(t, DebugMode, Mode())
-	flag.CommandLine = tmp
-
 	SetMode(DebugMode)
-	assert.Equal(t, debugCode, ginMode)
+	assert.Equal(t, int32(debugCode), atomic.LoadInt32(&ginMode))
 	assert.Equal(t, DebugMode, Mode())
 
 	SetMode(ReleaseMode)
-	assert.Equal(t, releaseCode, ginMode)
+	assert.Equal(t, int32(releaseCode), atomic.LoadInt32(&ginMode))
 	assert.Equal(t, ReleaseMode, Mode())
 
 	SetMode(TestMode)
-	assert.Equal(t, testCode, ginMode)
+	assert.Equal(t, int32(testCode), atomic.LoadInt32(&ginMode))
 	assert.Equal(t, TestMode, Mode())
 
 	assert.Panics(t, func() { SetMode("unknown") })
diff --git a/routergroup.go b/routergroup.go
index c833fe8f..b2540ec1 100644
--- a/routergroup.go
+++ b/routergroup.go
@@ -218,7 +218,7 @@ func (group *RouterGroup) createStaticHandler(relativePath string, fs http.FileS
 	fileServer := http.StripPrefix(absolutePath, http.FileServer(fs))
 
 	return func(c *Context) {
-		if _, noListing := fs.(*onlyFilesFS); noListing {
+		if _, noListing := fs.(*OnlyFilesFS); noListing {
 			c.Writer.WriteHeader(http.StatusNotFound)
 		}