fix: notFound() on missing post, await params for Next.js 15

lib/posts.ts

@@ -2,6 +2,7 @@ import fs from 'fs';
 import path from 'path';
 import matter from 'gray-matter';
 import readingTime from 'reading-time';
+import { notFound } from 'next/navigation';
 
 const postsDirectory = path.join(process.cwd(), 'posts');
 
@@ -90,6 +91,7 @@ export function getAllPostIds() {
 
 export async function getPostData(id: string): Promise<PostData> {
   const fullPath = path.join(postsDirectory, `${id}.mdx`);
+  if (!fs.existsSync(fullPath)) notFound();
   const fileContents = fs.readFileSync(fullPath, 'utf8');
   const matterResult = matter(fileContents);
   const stats = readingTime(matterResult.content);