The lambda execution is not suspending and the lambda container has no port exposed when running a java 11 lambda with the latest localstack docker image by docker-compose with the environment variable LAMBDA_JAVA_OPTS=-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=_debug_port_
    
It works fine for java8 runtime executions.

Docker command:

> localstack_1  | 2020-01-26T12:42:04:INFO:localstack.services.awslambda.lambda_executors: Running lambda cmd: CONTAINER_ID="$(docker create -i   -e ENV="$ENV" -e DOCKER_LAMBDA_USE_STDIN="$DOCKER_LAMBDA_USE_STDIN" -e HOSTNAME="$HOSTNAME" -e LOCALSTACK_HOSTNAME="$LOCALSTACK_HOSTNAME" -e AWS_LAMBDA_FUNCTION_TIMEOUT="$AWS_LAMBDA_FUNCTION_TIMEOUT" -e AWS_LAMBDA_FUNCTION_NAME="$AWS_LAMBDA_FUNCTION_NAME" -e AWS_LAMBDA_FUNCTION_VERSION="$AWS_LAMBDA_FUNCTION_VERSION" -e AWS_LAMBDA_FUNCTION_INVOKED_ARN="$AWS_LAMBDA_FUNCTION_INVOKED_ARN"  --rm "lambci/lambda:java11" "com.XXX.XXX.Handler")";docker cp "/tmp/localstack/zipfile.0c90736c/." "$CONTAINER_ID:/var/task"; docker start -ai "$CONTAINER_ID";

I think this is due to the fact that the classpath arguments and java opts are only being set if the rutime is equal to LAMBDA_RUNTIME_JAVA8 (line 211 of ocalstack/localstack/services/awslambda/lambda_executors.py , commit 03c6f4bf250edd18eb818ed65090f508636b0bff)
""" Create the final response for the given invocation result """
        if isinstance(result, Response):
            return result
        details = {
            'StatusCode': status_code,
            'Payload': result,
            'Headers': {}
        }
        if isinstance(result, dict):
            for key in ('StatusCode', 'Payload', 'FunctionError'):
                if result.get(key):
                    details[key] = result[key]
        
        was_json = False
        payload = details['Payload']
        if payload and isinstance(payload, POSSIBLE_JSON_TYPES) and payload[0] in JSON_START_CHARS:
            try:
                details['Payload'] = json.loads(details['Payload'])
                was_json = True
            except Exception:
                pass
        
        if details.get('FunctionError'):
            details['Headers']['X-Amz-Function-Error'] = str(details['FunctionError'])
        
        response_obj = details['Payload']
        if was_json or isinstance(response_obj, JSON_START_TYPES):