api/router/middleware/lang.go

package middleware

import (
	"github.com/gin-contrib/i18n"
	"github.com/gin-gonic/gin"
	"golang.org/x/text/language"
	"sikey.com/backend/internal/constant"
)

var translate = map[string]language.Tag{
	constant.Chinese:            language.Chinese,
	constant.ChinesetTaditional: language.TraditionalChinese,
	constant.ChineseHongKong:    language.TraditionalChinese,
	constant.ChineseTaiwan:      language.TraditionalChinese,
	constant.ChineseMacao:       language.TraditionalChinese,
	constant.Singapore:          language.SimplifiedChinese,
}

func Language() i18n.GetLngHandler {
	return func(ctx *gin.Context, defaultLng string) string {
		localization := ctx.GetHeader(constant.HeaderLocalization)
		if localization == "" {
			localization = defaultLng
		}

		// Translate to golang.org/x/text/language
		if local, ok := translate[localization]; ok {
			localization = local.String()
		}

		ctx.Set(constant.ContextValueLocalization, localization)
		return localization
	}
}