https://www.runatlantis.io/ is an open-source Golang project that listens for pull-request events via webhooks. You can define custom workflows (e.g, https://github.com/gruntwork-io/terragrunt ) and integrate it with other tools such as https://www.infracost.io/docs/integrations/atlantis/ .
The required token is a Bot User OAuth Token, under your App page on slack.
After placing the correct token, I had permission issues: initializing server: initializing webhooks: missing_scope
Create a Slack bot Create OAuth bot token (starts with xoxb-) Add the required permissions to the Scopes under OAuth & Permissions Place the configuration in your atlantis config.yaml