Add EventSource example

Port from extend/cowboy_examples.

examples/eventsource/src/eventsource_handler.erl

@@ -0,0 +1,27 @@
+%% Feel free to use, reuse and abuse the code in this file.
+
+%% @doc EventSource emitter.
+-module(eventsource_handler).
+
+-export([init/3]).
+-export([info/3]).
+-export([terminate/3]).
+
+init(_Transport, Req, []) ->
+	Headers = [{<<"content-type">>, <<"text/event-stream">>}],
+	{ok, Req2} = cowboy_req:chunked_reply(200, Headers, Req),
+	erlang:send_after(1000, self(), {message, "Tick"}),
+	{loop, Req2, undefined, 5000}.
+
+info({message, Msg}, Req, State) ->
+	ok = cowboy_req:chunk(["id: ", id(), "\ndata: ", Msg, "\n\n"], Req),
+	erlang:send_after(1000, self(), {message, "Tick"}),
+	{loop, Req, State}.
+
+terminate(_Reason, _Req, _State) ->
+	ok.
+
+id() ->
+	{Mega, Sec, Micro} = erlang:now(),
+	Id = (Mega * 1000000 + Sec) * 1000000 + Micro,
+	integer_to_list(Id, 16).