🌀 YACL - Yet Another Config Loader

YACL is a package designed to simplify configuration management in Go applications. It allows you to load and merge configuration from various sources such as environment variables, command-line flags, and multiple file formats into an arbitrary config structure instance. Also, it is designed to work out of the box with just a single line of code to load your configuration.

🌟 Features

Multiple sources to load config hierarchically:
- 🚩 Command-line flags
- 🌐 Environment variables
- 📜 YAML files
- 📄 JSON files
- 💾 Binary files
- 🆕 Default config instance (optional)
Automatically merges configs' fields with non-default values from different sources
Supports nested structs
Supports slices
No need to bind variables to config struct by hand
Easy-to-use single line convenient API
Aliases with the tag yacl: "newFieldName"

📝 Supported types

string
bool
uint32, uin64
int32, int64
float64
[]string
[]bool
[]uint32, []uint64
[]int32, []int64
[]float64

💻 Installation

go get github.com/andrew528i/yacl

🧑‍💻 Usage

Here's an example of how to use YACL to load configuration from multiple sources with just a single line of code.

import (
	"fmt"

	"github.com/andrew528i/yacl"
)

type DatabaseConfig struct {
	Hostname string
	Port     uint
}

type Config struct {
	Database     DatabaseConfig
	CanRestart   bool
	Tags         []string
	Temperatures []float64
}

func DefaultConfig() *Config {
	// Optional fallback struct with default values
	return &Config{
		Database:     DatabaseConfig{Hostname: "localhost-default"},
		CanRestart:   true,
		Tags:         []string{"hello", "world"},
		Temperatures: nil,
	}
}

func main() {
	cfg, err := yacl.Parse[Config](DefaultConfig()) // DefaultConfig() is optional
	// cfg, err := yacl.Parse[Config]()
	if err != nil {
		panic(err)
	}

	fmt.Printf("%+v\n", cfg)
}

YAML file

config.yaml content:

database:
  hostname: localhost-yaml
  port: 5432
can_restart: true
tags:
 - hello
 - world
temperatures:
 - 12.75
 - 17.49929
 - 27.46

$ ./app

&{Database:{Hostname:localhost-yaml Port:5432} CanRestart:true Tags:[hello world] Temperatures:[12.75 17.49929 27.46]}

Environment variables

$ export DATABASE_HOSTNAME=localhost-env
$ export DATABASE_PORT=1234
$ export CAN_RESTART=true
$ export TAGS=one,two
$ export TEMPERATURES=123.321,234.432,456.654
$ ./app

&{Database:{Hostname:localhost-env Port:1234} CanRestart:true Tags:[one two] Temperatures:[123.321 234.432 456.654]}

Command-line flags

$ ./app -database-hostname localhost-flags -database-port 6543 -can-restart -tags aaa -tags bbb -tags ccc -temperatures 1.223 -temperatures 2.332

&{Database:{Hostname:localhost-flags Port:6543} CanRestart:true Tags:[aaa bbb ccc] Temperatures:[1.223 2.332]}

Documentation

Global params

SetEnvPrefix

Use this to set a global prefix for environment variables:

yacl.SetEnvPrefix("APP")

For example, struct field HTTPPort uint will become APP_HTTP_PORT.

SetEnvDelimiter

yacl.SetEnvDelimiter("__")

For example, struct field HTTPPort uint will become HTTP__PORT.

SetFilePath

Specifies the path where to look for config files for all the formats: yaml, json, and bin. Also, YACL always looks for config files in the current working directory.

SetFilename

Sets the default filename for the config filename. For example:

yacl.SetFilename("my-config")

So YACL will look for those files: my-config.yaml, my-config.json, and my-config.bin.

SetFlagDelimiter

yacl.SetFlagDelimiter("_")

So, struct field DatabasePort uint will become command-line flag -database_port.

Parse

Parses all the config source hierarchically. See the usage section for more details and examples.

🌟 Instance parameters

In order to create a separate instance of YACL with its own params you can:

y := yacl.New()

SetEnvPrefix

Same as the global version.

SetEnvDelimiter

Same as the global version.

AddFilePath

Adds a path to look for a config.

SetFilename

Same as the global version.

SetFlagDelimiter

Same as the global version.

SetIgnoreFlags

In some cases, you may need not to touch flag params. For such a case, you can yacl.SetIgnoreFlags(true) and YACL will not clear default flags.

Parse

Same as the global version.