14. CLI & Libraries

Pick pragmatic libraries and structure CLIs for operability, testability, and cancellation.

Q1 Which libraries are sensible picks at middle level and why?

Answer:

• CLI: cobra/pflag;
• HTTP router: chi;
• logging: stdlib slog or zap for performance;
• metrics: prometheus/client_golang;
• tracing: otel;
• config: stdlib + optional viper/envconfig;
• migrations: golang-migrate; testing: stdlib + testify.

Explanation: These are widely adopted, well‑maintained, and easy to justify in interviews.

Q2 How do you structure a cobra CLI and handle cancellation?

Answer: Define a root command with persistent flags and subcommands. In RunE, accept a Context (cmd.Context()) and respect cancellation.

Explanation: Wire signal handling (signal.NotifyContext) at main and pass the context to command execution and downstream operations.