Feature/doc (#12)

* Updated README.md

* Updated version.

README.md

@@ -80,3 +80,68 @@ async def main():
         await generate_greeting("hello")
 asyncio.run(main())
 ```
+## Periodic Tasks
+Sometimes we need to run tasks periodically such as polling an external database or an 
+internal queue. We also want to make sure that when our application shuts down, it 
+gracefully tells the periodic tasks to stop starting new tasks but it waits for the 
+existing task to complete.
+```python
+import asyncio
+from asyncio_signal_bus import SignalBus
+
+BUS = SignalBus()
+@BUS.periodic_task(period_seconds=0.5)
+async def print_foos():
+     print("foo")
+
+async def main():
+     async with BUS:
+         await asyncio.sleep(2)
+asyncio.run(main())
+```
+### Period Tasks As Publishers
+Given that the periodic task is the furthest upstream in a process, we may use it to
+drive downstream subscribers. We can combine the periodic task with the injectors and 
+the publisher to periodically fetch data using configuration information and send it 
+to subscribers for processing.
+
+```python
+import asyncio
+from typing import List, Dict
+from asyncio_signal_bus import SignalBus
+import os
+
+BUS = SignalBus()
+
+async def get_url():
+    return os.environ.get("URL")
+
+async def get_secret():
+    return os.environ.get("SECRET")
+
+@BUS.periodic_task(period_seconds=1)
+@BUS.publisher(topic_name="new-data")
+@BUS.inject("url", get_url)
+@BUS.inject("secret", get_secret)
+async def get_data(url: str, secret: str):
+    # Perform some sort of IO here to get your data.
+    return [
+        {"id": 0, "value": "cats"},
+        {"id": 1, "value": "dogs"}
+    ]
+
+@BUS.subscriber(topic_name="new-data")
+async def process_values(data: List[Dict]):
+    for row in data:
+        print(row["value"].upper())
+
+@BUS.subscriber(topic_name="new-data")
+async def process_ids(data: List[Dict]):
+    for row in data:
+        print(row["id"] + 1)
+
+async def main():
+    async with BUS:
+        await asyncio.sleep(5)
+asyncio.run(main())
+```

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "asyncio-signal-bus"
-version = "1.5.0"
+version = "1.5.1"
 description = "Internal application publisher/subscriber bus using asyncio queues."
 authors = ["DustinMoriarty <[email protected]>"]
 readme = "README.md"