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)
if isinstance(e, ClientError):
            return e.get_response()
        return error_response('Unknown error: %s %s' % (e, traceback.format_exc()))
@app.route('%s/functions/<function>' % PATH_ROOT, methods=['GET'])
def get_function(function):
    """ Get details for a single function
        ---
        operationId: 'getFunction'
        parameters:
            - name: 'request'
              in: body
            - name: 'function'
              in: path
    """
    funcs = do_list_functions()
    for func in funcs:
        if func['FunctionName'] == function:
            result = {
                'Configuration': func,
                'Code': {
                    'Location': '%s/code' % request.url
                }
            }
            lambda_details = arn_to_lambda.get(func['FunctionArn'])
            if lambda_details.concurrency is not None:
                result['Concurrency'] = lambda_details.concurrency
            return jsonify(result)
    return not_found_error(func_arn(function))
@app.route('%s/functions/' % PATH_ROOT, methods=['GET'])
def list_functions():