keep the good language when going back in history

components/navigation/Language.vue

 <template>
 <div>
-    <select class="form-control" @change="saveLocale($event)" v-model="lang">
+    <select class="form-control" @change="saveLocale($event)" v-model="$i18n.locale">
         <option v-for="lang in $i18n.locales" :key="lang.code" :value="lang.code">{{ lang.name }}</option>
     </select>
 </div>
@@ -8,14 +8,9 @@
 
 <script>
 export default {
-    data() {
-        return {
-            lang: this.$i18n.locale
-        }
-    },
     methods: {
         saveLocale(e) {
-            this.lang = e.target.value
+            this.$i18n.locale = e.target.value
             this.$i18n.setLocaleCookie(e.target.value)
             this.$router.push(this.switchLocalePath(e.target.value))
         }