Lwt_main.Exit_hooksPromise-returning hooks, of type unit -> unit Lwt.t, that are called at process exit. Exceptions raised by these hooks are ignored.
type 'return_value kind = 'return_value Lwt.tHooks are functions of either type unit -> unit or unit -> unit Lwt.t; this type constructor is used only to express both possibilities in one signature.
Values of type hook represent hooks that have been added, so that they can be removed later (if needed).
Adds a hook to the hook sequence underlying this module, to be run first, before any other hooks already added.
Adds a hook to the hook sequence underlying this module, to be run last, after any other hooks already added.