Sometimes, you may encounter network problems, at this time, you need set proxy through daemon file of docker.

Daemon Config

The config file of docker located at: /etc/docker/daemon.json

If the config file doesn’t exit, you should create one.

And past the content below to the config file.

{
  "proxies": {
    "http-proxy": "http://proxy.example.com:3128",
    "https-proxy": "https://proxy.example.com:3129",
    "no-proxy": "*.test.example.com,.example.org,127.0.0.0/8"
  }
}

Restart Docker

sudo systemctl restart docker

Reference

https://docs.docker.com/engine/daemon/proxy/