use const http status text instead of a variable (#921)

src/webapi/router/router.go

@@ -17,8 +17,6 @@ import (
 	promstat "github.com/didi/nightingale/v5/src/webapi/stat"
 )
 
-var InternalServerError = "InternalServerError"
-
 func stat() gin.HandlerFunc {
 	return func(c *gin.Context) {
 		start := time.Now()

src/webapi/router/router_login.go

@@ -68,7 +68,7 @@ func logoutPost(c *gin.Context) {
 
 	delErr := deleteTokens(c.Request.Context(), metadata)
 	if delErr != nil {
-		ginx.NewRender(c).Message(InternalServerError)
+		ginx.NewRender(c).Message(http.StatusText(http.StatusInternalServerError))
 		return
 	}
 
@@ -118,7 +118,7 @@ func refreshPost(c *gin.Context) {
 		// Delete the previous Refresh Token
 		err = deleteAuth(c.Request.Context(), refreshUuid)
 		if err != nil {
-			ginx.NewRender(c, http.StatusUnauthorized).Message(InternalServerError)
+			ginx.NewRender(c, http.StatusUnauthorized).Message(http.StatusText(http.StatusInternalServerError))
 			return
 		}