gostructor

Consul KV — live config with blocking queries

Fills a struct from a Consul KV prefix and hot-reloads it when any key changes. The watch uses Consul blocking queries, so a change is picked up the instant it lands — no polling.

Run it

docker compose up -d     # dev-mode Consul, seeded with config/orders/*
go run .

You’ll see the seeded config, then change a key in another terminal:

docker compose exec consul consul kv put config/orders/host 10.0.0.9
docker compose exec consul consul kv put config/orders/tags "eu,fast,beta"

The program reloads immediately:

✅ 10.0.0.5:5432  level=info  tags=[eu primary]
✅ 10.0.0.9:5432  level=info  tags=[eu primary]
✅ 10.0.0.9:5432  level=info  tags=[eu fast beta]

Last-known-good

Each good read is written to ./snapshot. Stop Consul and rerun — the app still starts, serving the last snapshot instead of failing:

docker compose stop consul
go run .    # logs a warning, serves ./snapshot

Clean up

docker compose down
rm -rf snapshot

Key addressing

A field’s key is its base name joined onto the prefix: cfg:"host" → config/orders/host. Pin a different key with a per-source override: cfg:"host,consul:database/primary_host".

This site is open source. Improve this page.