config

Config Module

Configuration module based on Viper.

• Installation
• Documentation
  • Configuration files
  • Configuration usage
    • Configuration access
    • Configuration dynamic env overrides
    • Configuration env var placeholders
    • Configuration env var substitution

Installation

go get github.com/ankorstore/yokai/modules/config

Documentation

Configuration files

By default, the module expects configuration files:

• to be present in the root . or ./configs directories 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)

Also:

• the config file name and lookup paths can be configured
• the following configuration files format are supported: JSON, TOML, YAML, HCL, INI, and env file.

Configuration usage

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

# ./configs/config.yaml
app:
  name: app
  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

and the following *config.Config instance:

package main

import "github.com/ankorstore/yokai/modules/config"

var cfg, _ = config.NewDefaultConfigFactory().Create()

// equivalent to:
var cfg, _ = config.NewDefaultConfigFactory().Create(
  config.WithFileName("config"),          // config files base name
  config.WithFilePaths(".", "./configs"), // config files lookup paths
)

Configuration access

This module offers helper methods, as well as all Viper methods to access configuration values:

package main

import (
  "fmt"

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

func main() {
  // config
  cfg, _ := config.NewDefaultConfigFactory().Create()

  // helpers
  fmt.Printf("name: %s", cfg.AppName())         // name: app
  fmt.Printf("env: %s", cfg.AppEnv())           // env: dev
  fmt.Printf("version: %s", cfg.AppVersion())   // version: 0.1.0
  fmt.Printf("debug: %v", cfg.AppDebug())       // debug: false

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

Configuration 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.

package main

import (
  "fmt"
  "os"

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

func main() {
  // env vars
  os.Setenv("APP_ENV", "test")

  // config
  cfg, _ := config.NewDefaultConfigFactory().Create()

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

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

You can use any value for APP_ENV (to allow you to reflect your own envs): 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).

Configuration 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}.

package main

import (
  "fmt"
  "os"

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

func main() {
  // env vars
  os.Setenv("BAR", "bar")

  // config
  cfg, _ := config.NewDefaultConfigFactory().Create()

  // env var placeholder value
  fmt.Printf("placeholder: %s", cfg.GetString("config.placeholder")) // placeholder: foo-bar-baz
}

Configuration 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 CONFIG_SUBSTITUTION=bar env var will override the value from foo to bar.

package main

import (
  "fmt"
  "os"

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

func main() {
  // env vars
  os.Setenv("CONFIG_SUBSTITUTION", "bar")

  // config
  cfg, _ := config.NewDefaultConfigFactory().Create()

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