Elastic Search with Docker compose

I tried to bring up ES cluster with one node by ingesting some variables,it seems all the variables are not ingested. Is it issue with the syntax or that is how it works ?

Here is the compose file ( stripped down version)

version: '3.8'
services:
  elasticsearch1:
    image: docker.elastic.co/elasticsearch/elasticsearch:6.8.12
    container_name: elasticsearch1
    environment:
      - cluster.name=docker-cluster
      - node.name=elasticsearch1

However, i see only cluster.name is ingested.

training@training-virtualbox:~/playArea$ docker container exec -it elasticsearch1 sh
sh-4.2# cd config
sh-4.2# cat elasticsearch.
elasticsearch.keystore  elasticsearch.yml       
sh-4.2# cat elasticsearch.yml 
cluster.name: "docker-cluster"
network.host: 0.0.0.0