goconfig

Goconfig

goconfig is a lightweight Go library that fills structs from:

1. JSON config file
2. Environment variables
3. Command-line flags

It is designed for apps that want production-ready configuration with minimal boilerplate.

Installation

go get github.com/fulldump/goconfig

Quick Start

package main

import (
	"log"
	"time"

	"github.com/fulldump/goconfig"
)

type DB struct {
	Host string `usage:"Database host"`
	Port int    `usage:"Database port"`
}

type Config struct {
	ServiceName string        `usage:"Service name"`
	Timeout     time.Duration `usage:"Request timeout"`
	DB          DB
}

func main() {
	cfg := Config{
		ServiceName: "payments",
		Timeout:     5 * time.Second,
		DB: DB{
			Host: "localhost",
			Port: 5432,
		},
	}

	if err := goconfig.Load(&cfg); err != nil {
		log.Fatal(err)
	}
}

If you want legacy one-liner behaviour (exit on error):

goconfig.Read(&cfg)

Copy/Paste Recipes

1) API service

type Config struct {
	HTTPPort int           `usage:"HTTP port"`
	Timeout  time.Duration `usage:"Request timeout"`
	DB struct {
		Host string `usage:"Database host"`
		Port int    `usage:"Database port"`
	}
}

cfg := Config{HTTPPort: 8080, Timeout: 3 * time.Second}
if err := goconfig.Load(&cfg); err != nil {
	log.Fatal(err)
}

2) Worker service

type Config struct {
	Concurrency int           `usage:"Worker concurrency"`
	PollEvery   time.Duration `usage:"Polling interval"`
	Queues      []string      `usage:"Enabled queues"`
}

cfg := Config{Concurrency: 4, PollEvery: 2 * time.Second}
if err := goconfig.Load(&cfg); err != nil {
	log.Fatal(err)
}

Environment example:

export QUEUES='["emails", "billing"]'
export CONCURRENCY=8

3) CLI tool with deterministic args/env (tests)

cfg := Config{}
err := goconfig.Load(&cfg,
	goconfig.WithArgs([]string{"-verbose", "-config", "./testdata/config.json"}),
	goconfig.WithEnvLookup(func(k string) (string, bool) {
		if k == "VERBOSE" {
			return "true", true
		}
		return "", false
	}),
	goconfig.WithoutImplicitConfigFile(),
)

Precedence

Highest priority wins:

1. Command-line flags
2. Environment variables
3. JSON config file
4. Struct default values

If -config is not provided and ./config.json exists in the current working directory, goconfig loads it automatically before env vars and flags.

Naming Convention

Given this struct:

type Config struct {
	App struct {
		Port int
	}
}

• Flag name: -app.port
• Environment variable: APP_PORT
• JSON object:

{
  "app": {
    "port": 8080
  }
}

Built-in Flags

• -help: displays generated help with usage and env names
• -config: JSON file path to load before env and flags

When -config is not set, goconfig auto-loads config.json if it exists.

Supported Types

• bool
• string
• float32, float64
• int, int32, int64
• uint, uint32, uint64
• slices ([]T, as JSON arrays for env/flags)
• nested structs
• pointers to structs
• time.Duration (duration string like "15s" or nanoseconds)

Public API

Load

Load returns errors instead of exiting. This is the recommended API for libraries and services.

err := goconfig.Load(&cfg)

Optional behavior can be controlled with options:

• WithArgs([]string)
• WithProgramName("myapp")
• WithConfigFile("/etc/myapp/config.json")
• WithConfigFlagName("settings")
• WithImplicitConfigFile("myconfig.json")
• WithoutImplicitConfigFile()
• WithEnvLookup(func(string) (string, bool))

Read

Read keeps backward compatibility and exits process on error.

goconfig.Read(&cfg)

Why Teams Use goconfig

• Minimal integration cost for existing Go projects
• Predictable override order across local/dev/prod
• Built-in generated help for operations teams
• No external runtime dependencies

Development

go test ./...

For local workflows:

make test
make coverage

Open Source Health

• CI: GitHub Actions (.github/workflows/ci.yml)
• Contributing guide: CONTRIBUTING.md
• Code of conduct: CODE_OF_CONDUCT.md
• Security policy: SECURITY.md
• Changelog: CHANGELOG.md
• Release process: RELEASING.md
• Launch/promotion plan: PROMOTION_PLAN.md
• Issue and PR templates: .github/ISSUE_TEMPLATE and .github/pull_request_template.md

Contributing

Issues and pull requests are welcome.

Roadmap

See ROADMAP.md for the proposed adoption roadmap and high-impact issues.

License

MIT License. See LICENSE.