We released the latest version of the channel access token. This new version lets the user specify the expiration date and also provides security enhancements by switching to using a JSON Web Token (JWT) instead of the channel secret.
We recommend using the latest version of the channel access token.
Generate a JWT
You can use any JWT library or write your own code from scratch to Generate a JWT from your Assertion Signing Key. This is a necessary step in the Issue channel access token v2.1 API.
# New APIs
To learn the difference between the currently available channel access tokens, read Channel access tokens in the Messaging API documentation.