get host from http2 header during vite preview

Author: eltigerchino

packages/kit/src/exports/vite/preview/index.js

@@ -185,7 +185,7 @@ export async function preview(vite, vite_config, svelte_config) {
 
 		// SSR
 		vite.middlewares.use(async (req, res) => {
-			const host = req.headers['host'];
+			const host = req.headers[':authority'] || req.headers.host;
 
 			const request = await getRequest({
 				base: `${protocol}://${host}`,