I understand you have mongo running on Docker, so as a workaround you can use the same running container to connect:
docker exec -ti $container_name bash
bash-4.2$ mongo -u $MONGODB_USER -p $MONGODB_PASSWORD $MONGODB_DATABASE
MongoDB shell version v3.6.3
connecting to: mongodb://127.0.0.1:27017
MongoDB server version: 3.6.3
Ideally you could connect with just one command but I don't know why is failing when calling from outside:
# this fail but you can use with other databases
docker exec -ti $container_name mongo -u $MONGODB_USER -p $MONGODB_PASSWORD $MONGODB_DATABASE
The idea is simple, mongo is installed on the container so you tell docker to run from inside the container. If you need to load files from outside you always can mount a volume.