Configuration Guide

Go Conf Builder (V2) uses a declarative approach based on struct tags and pluggable sources.

Struct Tags

The conf tag is used to define how a field should be populated.

Multiple options are separated by commas:

Port int `conf:"env:PORT,flag:port,default:8080"`

Loader

The Loader is responsible for orchestrating the loading process from multiple sources.

l := loader.New(sources...)
err := l.Load(ctx, &myConfig)

Sources (Providers)

Sources implement the Provider interface and return a map[string]any.

Environment Variables

import "github.com/mirkobrombin/go-conf-builder/v2/pkg/source/env"

// Create with optional prefix
// If prefix is "APP", it will look for APP_PORT when tag is env:PORT
s := env.New("APP")

Command-line Flags

import "github.com/mirkobrombin/go-conf-builder/v2/pkg/source/flag"

// Reads from the standard library flag package
s := flag.New()

Custom Sources

You can implement your own source by fulfilling the Provider interface:

type Provider interface {
    Name() string
    Load(ctx context.Context) (map[string]any, error)
}

This allows loading configuration from files (YAML, JSON), remote stores (Etcd, Consul), or any other custom logic.

Type Support

The loader automatically converts source strings to the following field types:
- string
- int, int8, int16, int32, int64
- uint, uint8, uint16, uint32, uint64
- bool
- float32, float64