Stop server on SIGTERM by default

Fix #174

Author: yawaramin

example/z-playground/server/playground.ml

@@ -479,12 +479,6 @@ let rec gc ?(initial = true) () =
 let () =
   Dream.log "Starting playground";
 
-  (* Stop when systemd sends SIGTERM. *)
-  let stop, signal_stop = Lwt.wait () in
-  Lwt_unix.on_signal Sys.sigterm (fun _signal ->
-    Lwt.wakeup_later signal_stop ())
-  |> ignore;
-
   (* Build the base image. *)
   Lwt_main.run begin
     Lwt_io.(with_file ~mode:Output "Dockerfile" (fun channel ->
@@ -520,7 +514,7 @@ let () =
     Dream.html (Client.html example)
   in
 
-  Dream.run ~interface:"0.0.0.0" ~port:80 ~stop ~adjust_terminal:false
+  Dream.run ~interface:"0.0.0.0" ~port:80 ~adjust_terminal:false
   @@ Dream.logger
   @@ Dream.router [
 

src/dream.mli

@@ -2129,7 +2129,7 @@ val run :
     - [~stop] is a promise that causes the server to stop accepting new
       requests, and {!Dream.run} to return. Requests that have already entered
       the Web application continue to be processed. The default value is a
-      promise that never resolves.
+      promise that resolves when the [TERM] signal is received.
     - [~error_handler] handles all errors, both from the application, and
       low-level errors. See {!section-errors} and example
       {{:https://github.com/aantron/dream/tree/master/example/9-error#folders-and-files}

src/http/http.ml

@@ -668,7 +668,10 @@ let serve_with_maybe_https
 
 let default_interface = "localhost"
 let default_port = 8080
-let never = fst (Lwt.wait ())
+let on_sigterm =
+  let promise, resolve = Lwt.wait () in
+  ignore (Lwt_unix.on_signal Sys.sigterm (fun _ -> Lwt.wakeup_later signal_stop ()));
+  promise
 
 let network ~port ~socket_path =
   match socket_path with
@@ -679,7 +682,7 @@ let serve
     ?(interface = default_interface)
     ?(port = default_port)
     ?socket_path
-    ?(stop = never)
+    ?(stop = on_sigterm)
     ?(error_handler = Error_handler.default)
     ?(tls = false)
     ?certificate_file
@@ -707,7 +710,7 @@ let run
     ?(interface = default_interface)
     ?(port = default_port)
     ?socket_path
-    ?(stop = never)
+    ?(stop = on_sigterm)
     ?(error_handler = Error_handler.default)
     ?(tls = false)
     ?certificate_file