Dear OCaml people,
some time ago we encountered issues in the connection establishment of http-lwt-client in a GitHub action (using a pre-commit.com) hook. It was quite some journey from surfacing issue “HTTP connection timeout” to the actual issue, so we wrote it up at How we resolved the ‘HTTP request failed: timeout’ issue in OCaml – it reminds me of an issue surfacing as “bad record mac” in the TLS stack some years ago (see Catch the bug, walking through the stack).
This lead to the releases of happy-eyeballs{,-lwt,-mirage} 0.6.0 and dns* 7.0.3. In related news, we just release http-lwt-client 0.2.5 with further fixes (related to HTTP2) and http-mirage-client 0.0.5.
This debugging and fixing work was sponsored by semgrep.com – a great open source utility to statically analyse your codebase 
All the best, and please report issues and feedback either here, via eMail, or in the issue tracker(s). Enjoy your day!