try to inject the app in add_task method

sanic/app.py

@@ -88,6 +88,9 @@ class Sanic:
         """
         try:
             if callable(task):
+                try:
+                    self.loop.create_task(task(self))
+                except TypeError:
                     self.loop.create_task(task())
             else:
                 self.loop.create_task(task)
@@ -95,6 +98,9 @@ class Sanic:
             @self.listener('before_server_start')
             def run(app, loop):
                 if callable(task):
+                    try:
+                        loop.create_task(task(self))
+                    except TypeError:
                         loop.create_task(task())
                 else:
                     loop.create_task(task)

tests/test_create_task.py

@@ -2,6 +2,7 @@ from sanic import Sanic
 from sanic.response import text
 from threading import Event
 import asyncio
+from queue import Queue
 
 
 def test_create_task():
@@ -28,3 +29,19 @@ def test_create_task():
 
     request, response = app.test_client.get('/late')
     assert response.body == b'True'
+
+def test_create_task_with_app_arg():
+    app = Sanic('test_add_task')
+    q = Queue()
+
+    @app.route('/')
+    def not_set(request):
+        return "hello"
+
+    async def coro(app):
+        q.put(app.name)
+
+    app.add_task(coro)
+
+    request, response = app.test_client.get('/')
+    assert q.get() == 'test_add_task'