Give this a try
yarn add subsystem subsystem.fastify fastify
export const handle = (callContext: CallContext) => { callContext.output.body = 'hello world' } > routes/hello.ts
yarn subsystem -e hello
should see{ headers: {}, body: 'hello world' }
yarn subsystem -p subsystem.fastify
, wait a little bit and visithttp://localhost:3000/hello
, you should seehello world
as result