*** follow the steps ***
docker network create mongoNet
docker run -d -p 2001:27017 --net mongoNet --name r0 mongo --replSet mongoRepSet
docker run -d -p 2001:27017 --net mongoNet --name r1 mongo --replSet mongoRepSet
docker run -d -p 2001:27017 --net mongoNet --name r2 mongo --replSet mongoRepSet
docker exec -it r0 bash
config = {"_id": "mongoRepSet", "members": [{_id: 0, host: "192.168.1.100:2000"}, {_id: 1, host: "192.168.1.100:2001"}, {_id: 3, host: "192.168.1.100:2002"}]}
rs.initiate(config)