add example how to use AWSLambdaReceiver (slackapi#815)

examples/deploy-aws-lambda-receiver/.gitignore

@@ -0,0 +1,9 @@
+# node / npm
+node_modules/
+package-lock.json
+
+# macOS
+.DS_Store
+
+# Serverless
+.serverless/

examples/deploy-aws-lambda-receiver/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2020 Slack Technologies, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

examples/deploy-aws-lambda-receiver/README.md

@@ -0,0 +1,143 @@
+# Deploying to AWS Lambda ⚡️ Bolt for JavaScript
+
+> Slack app example for using the AWSLambdaReceiver of Bolt for JavaScript
+
+## Overview
+
+This is an example app that updates the [Getting Started ⚡️ Bolt for JavaScript app][bolt-app] to use the AWSLambdaReceiver and be deployed to [AWS Lambda][aws-lambda] using the [Serverless Framework][serverless-framework].
+You can learn how to build this example app by following our 📚 [Deploying to AWS Lambda guide][bolt-guide-aws-lambda].
+
+Before you begin, you may want to follow our [Getting Started guide][bolt-guide] to learn how to build your first Slack app using the [Bolt for JavaScript framework][bolt-website].
+
+## Getting started
+
+1. [Set up AWS credentials](#1-set-up-aws-credentials)
+1. [Set up local project](#2-set-up-local-project)
+1. [Create a Slack app](#3-create-a-slack-app)
+1. [Deploy to AWS Lambda](#4-deploy-to-aws-lambda)
+1. [Update Slack app settings](#5-update-slack-app-settings)
+1. [Test your Slack app](#6-test-your-slack-app)
+1. [Develop on local machine](#7-develop-on-local-machine)
+
+## 1. Set up AWS credentials
+
+### Install and configure AWS CLI
+
+Follow Amazon's guides to [install the AWS CLI v2 for macOS, Windows, or Linux][aws-cli-install] and [create a new IAM User][aws-cli-configure-user].
+
+When you have the AWS CLI and user credentials, then configure your local machine with the command:
+
+```zsh
+aws configure
+```
+
+## 2. Set up local project
+
+You can install the app's local development dependencies with the following command:
+
+```zsh
+npm install
+```
+
+You may also want to [install ngrok][ngrok-install] to start a local tunnel for local development.
+
+## 3. Create a Slack app
+
+### Create an app on api.slack.com
+
+1. Go to https://api.slack.com/apps
+1. Select **Create New App**
+    * Name your app, _don't worry you can change it later!_
+1. Select **OAuth & Permissions**
+    1. Scroll down to **Bot Token Scopes**
+    1. Add the following bot scopes:
+        1. Add the scope `app_mentions:read`
+        1. Add the scope `channels:history`
+        1. Add the scope `chat:write`
+        1. Add the scope `groups:history`
+        1. Add the scope `im:history`
+        1. Add the scope `mpim:history`
+    1. Select **Install App to Workspace** at the top of the page
+
+### Export environment variables
+
+```zsh
+export SLACK_SIGNING_SECRET=<your-signing-secret> # Slack app settings > "Basic Information"
+export SLACK_BOT_TOKEN=<your-xoxb-bot-token>      # Slack app settings > "OAuth & Permissions"
+```
+
+## 4. Deploy to AWS Lambda
+
+Run the following the command to deploy to AWS Lambda:
+
+```zsh
+npx serverless deploy
+# ...
+# endpoints:
+#  POST - https://d5c0t1xad4.execute-api.us-east-1.amazonaws.com/dev/slack/events
+```
+
+_Please note the endpoint `https://{your-domain}.amazonaws.com/dev/slack/events` because we'll use it in the next section._
+
+## 5. Update Slack app settings
+
+Now that your Slack app is deployed, you can register your AWS Lambda endpoint with the Slack API:
+
+1. Go to https://api.slack.com/apps
+1. Select your app
+1. Select **Event Subscriptions**
+    1. Enable **Events**
+    1. Set the **Request URL** to `https://{your-domain}.amazonaws.com/dev/slack/events`
+    1. Scroll down to **Subscribe to Bot Events**
+    1. Add the following bot events:
+        - `app_mention`
+        - `message.channels`
+        - `message.groups`
+        - `message.im`
+        - `message.mpim`
+    1. Select **Save Changes**
+
+## 6. Test your Slack app
+
+You can test your app by opening a Slack workspace and saying "hello" (lower-case):
+
+> 💬 hello
+>
+> 🤖 Hey there @Jane!
+
+_Remember, your app must be in the channel or DM where you say hello._
+
+## 7. Develop on local machine
+
+Open a terminal session to listen for incoming requests:
+
+```zsh
+npx serverless offline --noPrependStageInUrl
+```
+
+Open another terminal session to proxy Slack API requests locally:
+
+```zsh
+# -subdomain= is avalable only for paid accounts
+ngrok http 3000 -subdomain=my-unique-name
+```
+
+Update your [Slack app settings][slack-app-settings] to use your ngrok address:
+1. **Interactivity & Shortcuts**
+    1. Set the **Request URL** to `https://my-unique-name.ngrok.io/slack/events`
+1. **Event Subscriptions**
+    1. Set the **Request URL** to `https://my-unique-name.ngrok.io/slack/events`
+
+Follow the steps to [test your app](#6-test-your-slack-app).
+
+[aws-cli-install]: https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2.html
+[aws-cli-configure]: https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-quickstart.html
+[aws-cli-configure-user]: https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-quickstart.html#cli-configure-quickstart-creds
+[aws-lambda]: https://aws.amazon.com/lambda/
+[bolt-app]: https://github.com/slackapi/bolt-js-getting-started-app
+[bolt-guide]: https://slack.dev/bolt-js/tutorial/getting-started
+[bolt-guide-aws-lambda]: https://slack.dev/bolt-js/deployments/aws-lambda
+[bolt-website]: https://slack.dev/bolt-js/
+[ngrok-install]: https://api.slack.com/tutorials/tunneling-with-ngrok
+[serverless-framework]: https://serverless.com/
+[slack-app-settings]: https://api.slack.com/apps

examples/deploy-aws-lambda-receiver/app.js

@@ -0,0 +1,62 @@
+const { App, AwsLambdaReceiver } = require('@slack/bolt');
+
+// Initialize your custom receiver
+const awsLambdaReceiver = new AwsLambdaReceiver({
+  signingSecret: process.env.SLACK_SIGNING_SECRET,
+});
+
+// Initializes your app with your bot token and the AWS Lambda ready receiver
+const app = new App({
+  token: process.env.SLACK_BOT_TOKEN,
+  receiver: awsLambdaReceiver,
+  // The `processBeforeResponse` option is required for all FaaS environments.
+  // It allows Bolt methods (e.g. `app.message`) to handle a Slack request
+  // before the Bolt framework responds to the request (e.g. `ack()`). This is
+  // important because FaaS immediately terminate handlers after the response.
+  processBeforeResponse: true
+});
+
+// Listens to incoming messages that contain "hello"
+app.message('hello', async ({ message, say }) => {
+  // say() sends a message to the channel where the event was triggered
+  await say({
+    blocks: [
+      {
+        "type": "section",
+        "text": {
+          "type": "mrkdwn",
+          "text": `Hey there <@${message.user}>!`
+        },
+        "accessory": {
+          "type": "button",
+          "text": {
+            "type": "plain_text",
+            "text": "Click Me"
+          },
+          "action_id": "button_click"
+        }
+      }
+    ],
+    text: `Hey there <@${message.user}>!`
+  });
+});
+
+// Listens for an action from a button click
+app.action('button_click', async ({ body, ack, say }) => {
+  await say(`<@${body.user.id}> clicked the button`);
+
+  // Acknowledge the action after say() to exit the Lambda process
+  await ack();
+});
+
+// Listens to incoming messages that contain "goodbye"
+app.message('goodbye', async ({ message, say }) => {
+  // say() sends a message to the channel where the event was triggered
+  await say(`See ya later, <@${message.user}> :wave:`);
+});
+
+// Handle the Lambda function event
+module.exports.handler = async (event, context, callback) => {
+  const handler = await app.start();
+  return handler(event, context, callback);
+}

examples/deploy-aws-lambda-receiver/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "bolt-js-aws-lambda-receiver",
+  "version": "1.0.0",
+  "description": "Deploying to AWS Lambda ⚡️ Bolt for JavaScript using the AWSLambdaReceiver",
+  "main": "app.js",
+  "scripts": {
+    "start": "node app.js",
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "license": "MIT",
+  "dependencies": {
+    "@slack/bolt": "^3.2.0"
+  },
+  "devDependencies": {
+    "serverless": "^2.13.0",
+    "serverless-offline": "^6.8.0"
+  }
+}

examples/deploy-aws-lambda-receiver/serverless.yml

@@ -0,0 +1,17 @@
+service: serverless-lambda-receiver-bolt-js
+frameworkVersion: '2'
+provider:
+  name: aws
+  runtime: nodejs12.x
+  environment:
+    SLACK_SIGNING_SECRET: ${env:SLACK_SIGNING_SECRET}
+    SLACK_BOT_TOKEN: ${env:SLACK_BOT_TOKEN}
+functions:
+  slack:
+    handler: app.handler
+    events:
+      - http:
+          path: slack/events
+          method: post
+plugins:
+  - serverless-offline