How to configure docker compose so that nginx can forward requet to qgis-server?

I am new to qgis, and want to check how it works. So I setup a docker compose file with following content. The nginx shows connection refused

services:
  qgis-server:
    image: qgis/qgis-server:ltr
    container_name: qgis-server
    environment:
      - QGIS_SERVER_LOG_LEVEL=0
      - QGIS_PROJECT_FILE=/data/worldcities.csv
    volumes:
      - qgis_data:/data
    # ports: # with or without this there is no difference
    #   - "5555:5555"
    restart: unless-stopped
    networks:
      - qgis_network

  nginx:
    image: nginx:1.13
    container_name: nginx
    ports:
      - 8080:80
    restart: unless-stopped
    volumes:
      - ./conf/nginx.conf:/etc/nginx/conf.d/default.conf:ro
    depends_on:
      - qgis-server
    networks:
      - qgis_network

volumes:
  qgis_data:

networks:
  qgis_network:
    driver: bridge

where ./conf/nginx.conf contains configuration below that is copied from 8. Containerized deployment — QGIS Documentation documentation

server {
  listen 80;
  server_name _;
  location / {
    root  /usr/share/nginx/html;
    index index.html index.htm;
  }
  location /qgis-server {
    proxy_buffers 16 16k;
    proxy_buffer_size 16k;
    gzip off;
    include fastcgi_params;
    fastcgi_pass qgis-server:5555;
  }
}

docker logs –follow nginx displays errors in the log messages

connect() failed (111: Connection refused) while connecting to upstream, client: 172.30.0.1, server: _, request: "GET /qgis-server HTTP/1.1", upstream: "fastcgi://172.30.0.2:5555", host: "localhost:8080"

And here is snippet of the qgis-server logs. It looks like working without a problem.

02:48:51 INFO Server[25]: Adding service WMTS 1.0.0
02:48:51 INFO Server[25]: No cache strategy was specified. Using 'filesystem' as default.
02:48:51 INFO Server[25]: No cache strategy was specified. Using 'filesystem' as default.
02:48:51 INFO Server[25]: Initializing 'filesystem' cache strategy
02:48:51 INFO Server[25]: Server initialized
02:48:51 INFO ./src/server/qgsserverplugins.cpp[25]: load library /usr/lib/qgispython (3.44.11)
02:48:51 INFO ./src/server/qgsserverplugins.cpp[25]: Python support library loaded successfully.
02:48:51 WARNING Python error[25]: The extra plugin path '/io/plugins' does not exist!
02:48:51 INFO Server[25]: No server python plugins are available

I tried export port 5555:5555 in qgis-server, but the result is the same. How to fix this? Or what parameters should I adjust? Any advice? Thanks.