Small wrapper around the prom-client library to expose a /metrics endpoint
that reports on the express response middleware stack.
Has a placeholder mechanism for requiring default metric labels which would be fetched from the apps ECS context.
Uses on-finished and prom-client timers to measure how long each response
takes, also relied on by the express project.
Exposes the prom-client used by the library to allow other parts of the code
to record custom metrics which are uniformly reported by the /metrics endpoint.
npm i
npm start
curl http://localhost:8100/hello
curl http://localhost:8100/metrics