How to add pass a env variable as part of a json in Github Actions?

Question

I have the following steps as part of a Github Workflow:

run: |
    MESSAGE="${{ env.MESSAGE }}" && echo $MESSAGE \ &&
    curl -X POST -H 'Content-type: application/json' --data '{"text":$MESSAGE}' https://hooks.slack.com/services/<some_ids>

The echo works and outputs the correct message, but replacing the message in the json fails. What is the correct syntax?

I already tried escaping the quotes (it's not valid syntax):

--data '{"text":\"$MESSAGE\"}' 

Answer 1

you are putting your variable between simple quotes : --data '{"text":$MESSAGE}' which prevents interpolation of $MESSAGE .

you have to put $MESSAGE between double quotes: --data "{\\"text\\": $MESSAGE}"