Assuming no service is bound to 127.0.0.1:55000, the following minimal snippet will hang indefinitely.

  let cache = Cohttp_lwt_unix.Connection_cache.create ~parallel:1 () in
  Cohttp_lwt_unix.Connection_cache.call cache `GET
    (Uri.of_string "http://127.0.0.1:55000")

I quick look at the functor in Cohttp_lwt.Connection_cache and I guess the get_connection recursive function is to blame? I’ll try to dig deeper, but no matter the result of my search, I wanted to share my discovery.