Chaning the content of template file before deploying app-sync

Can we change the content of template file before deploy aws appsync?
For Example:
We need to use some value or codes from a json file in our vtl file. But since vtl files does not support feature. So we are thinking

“We should add a placeholder at places where we need that code, and during deployment, we replace those placeholder with the actual code in the generated pacakge, and then serverless will deploy it”


Why we are looking for such thing is mentioned in detailed here on Stackoverflow question