docs: add quickstart for Pub/Sub emulator

README.md

@@ -128,6 +128,31 @@ def function(request):
 This function will catch the `ZeroDivisionError` and return a different
 response instead.
 
+### Quickstart: With Pub/Sub Emulator
+
+1. Start Functions Frameworks in local development server listening on port 8082:
+   ```sh
+    functions-framework --target=hello --debug --port=8082
+   ```
+1. Start Pub/Sub Emulator.
+   ```sh
+    export PUBSUB_PROJECT_ID=abc
+    gcloud beta emulators pubsub start \
+        --project=$PUBSUB_PROJECT_ID \
+        --host-port=localhost:8080
+   ```
+1. Create a Pub/Sub topic and attach a push subscription to the topic, using `http://localhost:8082` as its push endpoint. Publish some messages to the topic. Observe your function getting triggered by Pub/Sub messages.
+   ```sh
+    export TOPIC_ID_=may
+    export PUSH_SUBSCRIPTION_ID=five
+    $(gcloud beta emulators pubsub env-init)
+    git clone https://github.com/googleapis/python-pubsub.git
+    cd python-pubsub/samples/snippets/
+    python publisher.py $PUBSUB_PROJECT_ID create $TOPIC_ID
+    python subscriber.py $PUBSUB_PROJECT_ID create $TOPIC_ID $PUSH_SUBSCRIPTION_ID http://localhost:8082
+    python publisher.py $PUBSUB_PROJECT_ID publish $TOPIC_ID
+   ```
+
 ### Quickstart: Build a Deployable Container
 
 1. Install [Docker](https://store.docker.com/search?type=edition&offering=community) and the [`pack` tool](https://buildpacks.io/docs/install-pack/).