I need to invoke a lambda function from another lambda function.

Instead of hard coding, the arn of a function resource section of custom-policies.json file of a serverless function in AWS amplify project, how can I use the intrinsic function such as GetAtt/Ref etc?

custom-policies.json

[
    {
        "Action": ["lambda:InvokeFunction"],
        "Resource": [
            "arn:aws:lambda:us-west-2:123456789012:function:my-function" // want to use function here, if possible.
        ],
        "Effect": "Allow"
    }
]