Config Module

Overview

Yokai provides a fxconfig module, allowing to define and retrieve configurations for your application.

It wraps the config module, based on Viper.

Installation

The fxconfig module is automatically loaded by Yokai's core.

When you use a Yokai application template, you have nothing to install, it's ready to use.

Configuration files

By default, the module expects the configuration files:

• to be present in the ./configs directory of your project
• to be named config.{format} (ex: config.yaml, config.json, etc.)
• to offer env overrides files named config.{env}.{format} based on the env var APP_ENV (ex: config.test.yaml if env var APP_ENV=test)

Supported configuration files formats: .json, .toml, .yaml, .hcl, .ini, and .env.

Usage

For the following examples, we will be considering those configuration files:

configs/config.yaml

app:
  name: app
  description: app description
  env: dev
  version: 0.1.0
  debug: false
config:
  values:
    string_value: default
    int_value: 0
  placeholder: foo-${BAR}-baz
  substitution: foo

and

configs/config.test.yaml

app:
  env: test
  debug: true
config:
  values:
    string_value: test

Configuration access

This module makes available the Config in Yokai dependency injection system.

It is built on top of Viper, see its documentation for more details about available methods.

To access it, you just need to inject it where needed, for example:

internal/service/example.go

package service

import (
    "fmt"

    "github.com/ankorstore/yokai/config"
)

type ExampleService struct {
    config *config.Config
}

func NewExampleService(config *config.Config) *ExampleService {
    return &ExampleService{
        config: config,
    }
}

func (s *ExampleService) PrintConfig() {
    // helpers
    fmt.Printf("name: %s", s.config.AppName())               // name: app
    fmt.Printf("description: %s", s.config.AppDescription()) // description: app description
    fmt.Printf("env: %s", s.config.AppEnv())                 // env: dev
    fmt.Printf("version: %s", s.config.AppVersion())         // version: 0.1.0
    fmt.Printf("debug: %v", s.config.AppDebug())             // debug: false

    // others
    fmt.Printf("string_value: %s", s.config.GetString("config.values.string_value")) // string_value: default
    fmt.Printf("int_value: %s", s.config.GetInt("config.values.int_value"))          // int_value: 0
}

Dynamic env overrides

This module offers the possibility to override dynamically (by merging) configuration files depending on the env var APP_ENV value.

For example, if APP_ENV=test, the module will use config.yaml values and merge / override them with config.test.yaml values.

If you run your application in test mode:

internal/service/example.go

// helpers
fmt.Printf("var: %s", s.config.GetEnvVar("APP_ENV")) // var: test

fmt.Printf("name: %s", s.config.AppName())               // name: app
fmt.Printf("description: %s", s.config.AppDescription()) // description: app description
fmt.Printf("env: %s", s.config.AppEnv())                 // env: test
fmt.Printf("version: %s", s.config.AppVersion())         // version: 0.1.0
fmt.Printf("debug: %v", s.config.AppDebug())             // debug: true

// others
fmt.Printf("string_value: %s", s.config.GetString("config.values.string_value")) // string_value: test
fmt.Printf("int_value: %s", s.config.GetInt("config.values.int_value"))          // int_value: 0

You can use any value for APP_ENV, to reflect your own environments names.

For example if APP_ENV=custom, the module will use config.yaml values and override them with config.custom.yaml values.

You just need to ensure that config.custom.yaml exists.

Env var placeholders

This module offers the possibility to use placeholders in the config files to reference an env var value, that will be resolved at runtime.

Placeholder pattern: ${ENV_VAR_NAME}.

For example, with the env var BAR=bar:

internal/service/example.go

// placeholder: foo-bar-baz
fmt.Printf("placeholder: %s", s.config.GetString("config.placeholder"))

Env var substitution

This module offers the possibility to perform configuration files values substitution from env var values.

For example, if you have a configuration key config.substitution=foo, providing the env var CONFIG_SUBSTITUTION=bar will override the value from foo to bar.

internal/service/example.go

// substitution: bar
fmt.Printf("substitution: %s", cfg.GetString("config.substitution"))