Improve asyncio instrumentation examples

Author: andremm

instrumentation/opentelemetry-instrumentation-asyncio/src/opentelemetry/instrumentation/asyncio/__init__.py

@@ -41,6 +41,11 @@ async def main():
 
     # export OTEL_PYTHON_ASYNCIO_FUTURE_TRACE_ENABLED=true
 
+    import asyncio
+    from opentelemetry.instrumentation.asyncio import AsyncioInstrumentor
+
+    AsyncioInstrumentor().instrument()
+
     loop = asyncio.get_event_loop()
 
     future = asyncio.Future()
@@ -52,6 +57,8 @@ async def main():
 -------------
 .. code:: python
 
+    # export OTEL_PYTHON_ASYNCIO_TO_THREAD_FUNCTION_NAMES_TO_TRACE=func
+
     import asyncio
     from opentelemetry.instrumentation.asyncio import AsyncioInstrumentor