num30/config

Declarative configuration for Go

Description

config is a package that supports reading configuration into a struct from files, environment variables and command-line arguments. All you need is to declare a structure that will hold your configuration and call `Read` method. The library will pool the values from a config file in any well-known format, from env vars that follows simple naming convention, or from command-line arguments

Programming language: Go

License: MIT License

Tags: Configuration     CLI     Files     Go     Package     Golang     Environment     Library    

README

Declarative configuration for Go :rocket:

Features

• declarative way of defining configuration
• reading configuration from file, environment variables or command line arguments in one lines of code
• validation

Example

config is a package that supports reading configuration into a struct from files, environment variable and command line arguments. All you need is to declare a config structure and call Read method.

type Config struct {    
    DB                Database  
    Debug             Debug
}

type Database struct {
    Host       string
    Password   string
    DbName     string
    Username   string
    Port       int
}

func main() {
    var config Config 
    err := config.NewConfReader("myconf").Read(&config) 
    if err != nil {
        panic(err)
    }
}

When you want to change, for example, DB Host of your applications you can do any of the following:

1. create config myconf.yaml file in home directory db: host: "localhost"
2. set environment variable. Like DB_HOST=localhost
3. set command line argument. Like --db.host=localhost

:information_source: Refer to the example that illustrates how to use ConfReader.

Execute go run examples/main.go to run the example.

Install :package:

go get github.com/num30/config  

Setting Configuration Values :construction_worker:

ConfReader merges values from all three sources in the following order:

1. File
2. Environment variables
3. Command line arguments

Setting same key in file will be overridden by environment variable and command line argument has the highest priority. However, you can set one key in file and other in env vars or command line args. Those will be merged.

Config File :memo:

Name

ConfReader will use config name property to search for a config file with that name.

Location

By default, config reader will search for a config file in home or in current directory. You can override this behavior by using NewConfReader("myconf").WithSearchDirs("/etc/conf") of config builder

Referring fields

Field names are converted from camel case starting with lower case letter. For example if it code you refer to value as DB.DbName then it will be converted to

db:
   dbName: "mydb"

Format

Config file type could be any type supported by viper: JSON, TOML, YAML, HCL, INI, envfile and Java Properties files.

Environment Variables :package:

To set a flag via environment variable, make all letters uppercase and replace '.' with '_' in path. For example: app.Server.Port -> APP_SERVER_PORT

Environment variables are prefixed with config name by default. For example NewConfReader("myconf") will search for environment variables like MYCONF_DB_HOST This behavior could be overridden by setting NewConfReader("myconf").WithoutPrefix()

Command Line Arguments :computer:

To set a configuration field via command line argument you need to pass and argument prefixes wiht -- and lowercase field name with path. Like --db.host=localhost Boolean value could be set by passing only flag name like --verbose

You can override name for a flag by using tag flag:"name" on a field. For example:

type Config struct {        
    DebugMode             bool `flag:"debug"`
}

You can set the flag by calling myapp --debug

Validations :underage:

You can validate fields of you configuration struct by using validate tag. For example:

type Config struct {        
    Host           string `validate:"required"`
}

If validation fails ConfReader.Read will return an error.

Contributing :clap:

We love help! Contribute by forking the repo and opening a pull requests or by creating an issue.

Credits :star:

This package is based Viper Special thanks:

• enviper for making environment variables work with viper
• defaults for making default values work with structures