Invalid Read on closed Body with certain bodies

### Welcome! - [x] Yes, I've searched similar issues on [GitHub](https://github.com/traefik/whoami/issues) and didn't find any. ### What did you do? When doing a HTTP POST a request with a certain body ``` POST /aze HTTP/1.1 Accept: */* Accept-Encoding: gzip, deflate, br Connection: keep-alive Content-Type: multipart/form-data; boundary=d1151a93a3007ebf-f02190187c44a8c6-bd59b64781bf3c60-cc7681c349f84180 Host: XXXXX:2222 User-Agent: xh/0.22.2 --d1151a93a3007ebf-f02190187c44a8c6-bd59b64781bf3c60-cc7681c349f84180 Content-Disposition: form-data; name="body"; filename="test.yml" test: azertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazerty test: azertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazerty test: azertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazerty test: azertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazerty --d1151a93a3007ebf-f02190187c44a8c6-bd59b64781bf3c60-cc7681c349f84180-- ``` the whoami server returns `http: invalid Read on closed Body` Returned body: ``` HTTP/1.1 200 OK Content-Type: text/plain; charset=utf-8 Date: Sun, 23 Mar 2025 22:45:19 GMT Transfer-Encoding: chunked Hostname: XXXXX IP: XXXXX IP: XXXXX IP: XXXXX IP: XXXXX IP: XXXXX IP: XXXXX IP: XXXXX RemoteAddr: XXXXX POST /aze HTTP/1.1 Host: XXXXX:2222 User-Agent: xh/0.22.2 Content-Length: 602 Accept: */* Accept-Encoding: gzip, deflate, br Connection: keep-alive Content-Type: multipart/form-data; boundary=d1151a93a3007ebf-f02190187c44a8c6-bd59b64781bf3c60-cc7681c349f84180 --d1151a93a3007ebf-f02190187c44a8c6-bd59b64781bf3c60-cc7681c349f84180 Content-Disposition: form-data; name="body"; filename="test.yml" test: azertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazerty test: azertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazerty test: azertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazerty test: azertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazertyazerhttp: invalid Read on closed Body ``` ### What were you expecting? The body should be returned without a `http: invalid Read on closed Body` error ### What version are you using? v1.11.0 ### What is your environment & configuration? ` ./whoami -port 2222 -verbose` ### If applicable, please paste the log output in DEBUG level 2025/03/23 23:45:19 http: superfluous response.WriteHeader call from main.whoamiHandler (app.go:242) 2025/03/23 23:45:19 127.0.0.1:41320 - - [23/Mar/2025:23:45:19 +0100] "POST /aze HTTP/1.1" - -