only specify host port for postgres container

Author: jordanstephens

samples/rails/compose.yaml

@@ -27,7 +27,8 @@ services:
       POSTGRES_USER: rails_user
       POSTGRES_PASSWORD: secret
     ports:
-      - "5432:5432"
+      - mode: host
+        target: 5432
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -U app_user"]
       interval: 10s