08-webservice.md

Full service config

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The big one: everything at once, at production scale. The webservice example assembles a realistic microservice config — ~30 fields across nested sub-structs (server, database, redis, logging, auth) — from a JSON base + env overrides + gos defaults, with masked secrets and a focused resolution trace.

It's the combination of every other feature page:

• Two tags naming and shaping each field,
• Priority — env overrides layered over a JSON base over defaults,
• Sources — JSON file + env + default composed with WithSources,
• Field types — durations, bools, ints, nested structs,
• Observability & masking — a trace with secrets masked.

Try it

go run ./examples/webservice

Output:

payments-api v1.8.3 starting in "production"
  listen:   0.0.0.0:443  (TLS true)
  database: app@prod-db.internal:5432/payments (pool 50, password set: 12 chars)
  redis:    redis.internal:6379 (pool 20)
  logging:  level=warn format=json sample=0.25
  auth:     issuer=https://auth.internal ttl=30m0s

── resolution trace (who won each field; secrets masked) ──
Configuring main.Config: 32 fields
[Primary Source] json (loaded 16 fields)
[Defaults] applied for 8 fields

Overrides & Secrets:
  Environment string  ⇐ env (override) = production
  Version     string  ⇐ env (override) = 1.8.3
  Port        int     ⇐ env (override) = 443
  Host        string  ⇐ env (override) = prod-db.internal
  Password    string  ⇐ env = •••-pw (secret)
  LogLevel    string  ⇐ env (override) = warn
  JWTSecret   string  ⇐ env = •••key (secret)

Sixteen fields come from the JSON base, eight from defaults, and a handful of operator env vars override the rest — with Password and JWTSecret masked in the trace but real on the struct. This is what a production Configure call looks like end to end.