I did this

curl https://junkrat.kozea.fr/test_curl

I expected the following

Curl correctly returns the content of the page, but then adds curl: (56) Unexpected EOF or curl: (16) Error in the HTTP2 framing layer. Other clients such as wget, Chrome or Firefox don't hit the same error. It also works well when curl uses HTTP/1.1 instead of HTTP/2.0.

The server behind https://junkrat.kozea.fr/test_curl is nginx, and the request reloads the configuration of nginx. According to nginx's documentation, reloading its configuration should gracefully handle the current requests. I don't know if the problem comes from the server or from the client, but as the other clients don't show the error, there may be something wrong in curl.

curl/libcurl version

curl 7.54.1 (x86_64-pc-linux-gnu) libcurl/7.54.1 OpenSSL/1.0.2l zlib/1.2.11 libssh2/1.8.0 nghttp2/1.23.1
Release-Date: 2017-06-14
Protocols: dict file ftp ftps gopher http https imap imaps pop3 pop3s rtsp scp sftp smtp smtps telnet tftp
Features: AsynchDNS IPv6 Largefile NTLM SSL libz TLS-SRP HTTP2 UnixSockets HTTPS-proxy

I get the same result with the current version of Debian Stretch's curl.

operating system

Linux 4.11.7-gentoo #2 SMP Mon Jun 26 10:45:58 CEST 2017 x86_64 Intel(R) Core(TM) i7-6500U CPU @ 2.50GHz GenuineIntel GNU/Linux