Yup this was the problem. There is no dgraph:latest container. Changed it to graph:master. and it started working. But then when i tried to upload schema it returned this message
resolving updateGQLSchema failed because unauthorized ip address: 172.18.0.1
Then I added this part to alpha command
--security "whitelist=172.18.0.1"
and afer that it started giving me the same errors as before.
E0301 12:30:10.913978 19 groups.go:1148] Error during SubscribeForUpdates for prefix "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x15dgraph.graphql.schema\x00": error from client.subscribe: rpc error: code = Unavailable desc = connection closed. closer err: <nil>