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)
from localstack.services.awslambda.lambda_executors import (
    LAMBDA_RUNTIME_PYTHON27,
    LAMBDA_RUNTIME_PYTHON36,
    LAMBDA_RUNTIME_NODEJS,
    LAMBDA_RUNTIME_NODEJS610,
    LAMBDA_RUNTIME_NODEJS810,
    LAMBDA_RUNTIME_JAVA8,
    LAMBDA_RUNTIME_JAVA11,
    LAMBDA_RUNTIME_DOTNETCORE2,
    LAMBDA_RUNTIME_DOTNETCORE21,
    LAMBDA_RUNTIME_GOLANG,
    LAMBDA_RUNTIME_RUBY,
    LAMBDA_RUNTIME_RUBY25,
    LAMBDA_RUNTIME_CUSTOM_RUNTIME)
from localstack.utils.common import (to_str, load_file, save_file, TMP_FILES, ensure_readable,
    mkdir, unzip, is_zip_file, zip_contains_jar_entries, run, short_uid, timestamp,
    TIMESTAMP_FORMAT_MILLIS, md5, parse_chunked_data, now_utc, safe_requests,
    isoformat_milliseconds)
from localstack.utils.analytics import event_publisher
from localstack.utils.aws.aws_models import LambdaFunction
from localstack.utils.cloudwatch.cloudwatch_util import cloudwatched
APP_NAME = 'lambda_api'
PATH_ROOT = '/2015-03-31'
ARCHIVE_FILE_PATTERN = '%s/lambda.handler.*.jar' % config.TMP_FOLDER
LAMBDA_SCRIPT_PATTERN = '%s/lambda_script_*.py' % config.TMP_FOLDER
LAMBDA_RUNTIMES = [LAMBDA_RUNTIME_PYTHON27, LAMBDA_RUNTIME_PYTHON36,
    LAMBDA_RUNTIME_DOTNETCORE2, LAMBDA_RUNTIME_DOTNETCORE21, LAMBDA_RUNTIME_NODEJS,
    LAMBDA_RUNTIME_NODEJS610, LAMBDA_RUNTIME_NODEJS810, LAMBDA_RUNTIME_JAVA8, LAMBDA_RUNTIME_RUBY,
    LAMBDA_RUNTIME_RUBY25]
LAMBDA_DEFAULT_TIMEOUT = 3