docker-compose.file

version: '3'
services:
  my-gotest:
    container_name: testProject
    image: hub.docker.com/benben/my-gotest:test
    restart: always
    ports:
      - 8080:8080
    networks:
      - bennet
networks:
  bennet:
    external: true

如果在docker-compose文件中设置external为true，那么使用docker-compose up -d来启动服务时，首先docker引擎会查找external声明的网络，找到后进行连接。否则会提示错误：

ERROR: Network bennet declared as external, but could not be found. Please create the network manually using `docker network create bennet` and try again.

当其值为false时，会自动创建一个testProject_bennet的网络，如果没有networks字段时，会创建一个testProject_default的网络。