Glossary: Go in Practice

Host addresses (127.0.0.1, 0.0.0.0)

Also written: 127.0.0.1, 0.0.0.0, localhost

127.0.0.1 (`localhost`) is the machine itself, reachable only from that machine; 0.0.0.0 (or an address with no host, like `:8081`) listens on every network interface. Inside a container, `localhost` is the container, so a published port needs `:8081`.