What event struct should I be using for CloudTrail?

My use case is that I want to post CloudTrail events to my company's Slack so I can see who is logging in etc. I think this is possible from Creating a Trail and assigning to my Golang function, e.g.

I can't seem to see a corresponding struct to map this event onto:
https://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-event-reference-aws-console-sign-in-events.html