docs: fastify reads the body for you [skip ci]

Author: enisdenjo

README.md

@@ -190,11 +190,7 @@ fastify.all('/graphql', async (req, res) => {
       url: req.url,
       method: req.method,
       headers: req.headers,
-      body: await new Promise((resolve) => {
-        let body = '';
-        req.on('data', (chunk) => (body += chunk));
-        req.on('end', () => resolve(body));
-      }),
+      body: req.body, // fastify reads the body for you
       raw: req,
     });
     res.writeHead(init.status, init.statusText, init.headers).end(body);