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Kenta Takeuchi
Kenta Takeuchi

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Implement Slash Command for Slack App using Cloud Functions

This articles is a translation of Cloud Functionsを使ってSlack AppのSlash Commandを実装


Implement Slash Command for Slack App using Cloud Functions.

Here is the boilerplate I made.


There are various ways to create a Slack App that can use Slash Command, but I decided to use CloudFront Functions because it's cheap, easy, and serverless.


  • Availability of Google Cloud Platform
  • gcloud command setup completed
    • the gcloud command must be available to deploy the application
  • Cloud Build API enabled
    • I need to build a function to deploy it to Cloud Functions.

create a function in Cloud Functions

Create a function in the Cloud Functions console.
Select HTTP for the trigger type, Allow unauthenticated calls for authentication, and check HTTPS required.

Make a note of the trigger URL described in Cloud Functions Function Details > Triggers later after deploying the function.

Preparing the Slack App

Create a Slack App

In Create an app, press From scratch.

Screenshot 2022-09-04 17 29 50

Enter App Name.

Select a workspace with Pick a workspace to develop your app in:
Press Create App.

Screenshot 2022-09-04 17 32 07

Set Slash Command

On the setting screen (ex.*****), select Slash Commands.

Screenshot 2022-09-04 17 33 21

Press Create New Command and optionally enter Command, Short Description, Usage Hint, Escape channels, users, and links sent to your app.

For Request URL, enter the trigger URL you made a note of earlier.
The trigger URL has the format

Screenshot 2022-09-04 17 35 59

After entering, press Save.

Install the Slack App

On the setting screen (ex.*****), press Install App.

Screenshot 2022-09-04 17 37 16

Press Install to workspace to install Appwo in any workspace.

Get the Signing Secret

On the setting screen (ex.*****), press Basic Information.

There is Signing Secret in the item called App Credentials, so make a note of the value.

implement the function

Implement functions that deploy to Cloud Functions.

There are some addictive parts (such as the go mod vendor part), but I will omit the implementation details.

See below for the source code.


deploy the function

Prepare environment variables according to the README of go-slack-app-on-cloud-functions-boilerplate and deploy.

Operation check

Try using the created Slash Command in Slack.

/hello Bob

Screenshot 2022-09-04 17 47 11


I'd love to be able to code the part that makes a Slack App.


I wanted to create a Slack Command for attendance management at work go-slack-app-on-cloud-functions-boilerplate, I made akashi-slack-slash-command.

In this implementation, the storage is Spreadsheet, but when using Google Workspace, there is a management problem that Spreadsheet sharing settings cannot be flexibly adjusted around permissions, so at work, the storage is replaced from Spreadsheet to Cloud Storage I adjusted the implementation and used it.

If there is an organization that uses Akashi for attendance management and Slack for chat tools, I think Slack Command can be used easily.

It doesn't cost much to operate, and the scalability may be a bit questionable.

I think that it can probably be used without problems unless it is an organization with more than a few thousand people.

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