Error "The security token included in the request is invalid" invoking lambda function url

Hi,

This is the follow up of this question - https://repost.aws/questions/QUE8NpRj91RW-9p1MiOv9iYQ/calling-iam-auth-function-urls-from-lambda

I am trying to invoke the lambda with function url (lets name this as "funcUrlLambda" ) from another lambda (lets say this as "apiGwLambda"). I have given apiGwLambda role permission in funcUrlLambda. In apiGwLambda, I am doing the signv4 with the access key and secret key from lambda env variables.

For signV4, I am using the code from these links https://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-examples-using-sdks.html#sig-v4-examples-using-sdk-java https://docs.aws.amazon.com/AmazonS3/latest/API/samples/AWSS3SigV4JavaSamples.zip

But I am getting this error {"message":"The security token included in the request is invalid."} from funcUrlLambda. It would be super helpful if some one could provide help on this ?

Code getting the access key and secret key in lambda

        val accessKey = System.getenv("AWS_ACCESS_KEY_ID")
        val secretKey = System.getenv("AWS_SECRET_ACCESS_KEY")