fix(gin): data race warning for gin mode (#1580)

* fix: data race warning (#1180)

* Fix the tests

* refactor: remove unnecessary imports and optimize codebase

- Remove unnecessary import of `flag`

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* test: refactor test assertions for mode settings

- Update test assertions for mode setting in `mode_test.go`

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

---------

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>
Co-authored-by: Bo-Yi Wu <appleboy.tw@gmail.com>

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)
 }