Fix default lang bug when React tree doesn't contain withI18next

example/nextjs/pages/_app.js

@@ -31,8 +31,16 @@ if (enableSubpaths) {
 // Warning: Did not expect server HTML to contain a <h1> in <div>.
 // not sure - did neither find something wrong - nor seems the warning to make sense
 export default class MyApp extends App {
+
+  static async getInitialProps({ ctx }) {
+    return {
+      initialLanguage: ctx.req.language ?
+        ctx.req.language : translation.defaultLanguage
+    };
+  };
+
   render() {
-    const { Component, pageProps } = this.props;
+    const { Component, pageProps, initialLanguage } = this.props;
 
     return (
       <Container>
@@ -41,6 +49,7 @@ export default class MyApp extends App {
           ns="common"
           i18n={(pageProps && pageProps.i18n) || i18n}
           wait={process.browser}
+          initialLanguage={initialLanguage}
         >
           {t => (
             <React.Fragment>