This describes how to get and access token from the Goa library as described in Oauth2 for Apps Script in a few lines of code (which you should read first for background).
If you have initialized the credentials as described in Goa Setup, and gone through the process of the Goa Authentication dialog you are now ready to use the token or refreshed tokens with no further dialogs required.
This example does a query using the reddit API.

getting the token

consuming the token

The consent screen code

As described in Authentication dialog, you can simply leave the doGet() dialog in place instead of using this pattern, but using this simplified pattern allows you to unpublish the web app.

For more like this, see Oauth2 for Apps Script in a few lines of code.

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