fix async run

sanic/server.py

@@ -297,8 +297,8 @@ def serve(host, port, request_handler, error_handler, before_start=None,
     :param protocol: Subclass of asyncio protocol class
     :return: Nothing
     """
-    loop = async_loop.new_event_loop()
-    asyncio.set_event_loop(loop)
+    loop = asyncio.get_event_loop()
+    asyncio.set_event_loop_policy(async_loop.EventLoopPolicy())
 
     if debug:
         loop.set_debug(debug)

tests/test_loop_policy.py

@@ -0,0 +1,27 @@
+from sanic import Sanic
+import asyncio
+from signal import signal, SIGINT
+import uvloop
+
+
+def test_loop_policy():
+    app = Sanic('test_loop_policy')
+
+    server = app.create_server(host="0.0.0.0", port=8000)
+
+    loop = asyncio.get_event_loop()
+    task = asyncio.ensure_future(server)
+    signal(SIGINT, lambda s, f: loop.close())
+
+    # serve() sets the event loop policy to uvloop but
+    # doesn't get called until we run the server task
+    assert isinstance(asyncio.get_event_loop_policy(),
+                      asyncio.unix_events._UnixDefaultEventLoopPolicy)
+
+    try:
+        loop.run_until_complete(task)
+    except:
+        loop.stop()
+
+    assert isinstance(asyncio.get_event_loop_policy(),
+                      uvloop.EventLoopPolicy)