12 Factor App Logging. In a simple app on one server, you have more flexibility in how you want to approach this. Logs provide visibility into the behavior of a running app.
Further, deciding how you work with logs needs to be part of a larger apm and/or paas strategy. Use declarative formats for setup automation, to minimize time and cost for new developers joining the project. Stackdriver logging if you’re using google cloud, and elasticsearch if you’re not.
Instead of including code in a microservice for routing or storing logs, use one of the many good log‑management solutions on the market, several of which are listed in the twelve‑factor app.
Review the google cloud product suite for logging and monitoring; Review the google cloud product suite for logging and monitoring; What is 12 factor app design methodology? Previous versions (5.x & 6.x) references.