Part 4 of Goose, then any language on Flisk. docs/byo.md says any app that fits the contract can run as a bring-your-own resource. Fastify is the worked example because it needs nothing beyond the framework. Node, Go, Rust, Java, Ruby, and Goose use the same command. Flisk does not generate the application.

The contract, for whatever language you brought

Listen on the port in service.json . Compose sets PORT . It also sets DATABASE_URL in every BYO container. Read PORT . Ignore DATABASE_URL unless you asked for Postgres.

Bind 0.0.0.0 .

Answer HTTP 200 on healthCheckPath if it speaks HTTP. --health-path /health . This type does not get a Compose curl probe.

Provide a Dockerfile or --image . COPY paths are relative to the resource directory.

Ports are 4000–5999. If a Dockerfile already exists, Flisk keeps it. If you register with no Dockerfile, Flisk writes an Nginx placeholder. Write yours first.

Goose's standard library can read PORT with os.env . Sockets are not in v1.…