Communication between docker compose containers, unable to connect to MySQL

Docker compose deployment golang, mysql, remote, 127.0.0.1 can access the container mysql, but the go container can not connect. Docker- compose.yaml The documents are as follows:

version: '2'
services:
  order_mysql:
    networks:
      - test_network
    image: mysql
    command: --default-authentication-plugin=mysql_native_password 
    container_name: "order_mysql"
    ports:
      - "3333:3306"
    expose:
      - "3306"
    environment:
      MYSQL_DATABASE: order
      MYSQL_USER: root
      MYSQL_PASSWORD: 123456
      TZ: Asia/Shanghai 
    restart: always
    volumes:
      - "./mysql/db:/var/lib/mysql"
      - "./mysql/conf/my.cnf:/etc/my.cnf"
      - "./mysql/init:/docker-entrypoint-initdb.d/"

  order_redis:
    image: redis
    command: --requirepass 12345678
    container_name: "order_redis"
    ports:
      - "6666:6379"
    volumes:
      - "./redis:/var/lib/redis"
    networks:
      - test_network
  order_golang:
    depends_on:
      - order_mysql
      - order_redis
    build: .
    ports:
      - "2020:2020"
    tty: true
    networks:
      - test_network
    links:
      - order_mysql:order_mysql
      - order_redis:order_redis

networks:
  test_network:
  

Host uses the alias order_ MySQL address, network segment also assigned, order_ There is no problem in compiling golang container. Why can't the container connect to MySQL

dial tcp 172.21.0.2:3306: connect: connection refused