Goconfig

goconfig is a lightweight library that populates your Go structs from command line flags, environment variables and JSON configuration files. It aims to make configuration straightforward while keeping your code idiomatic.

Features

• Unified configuration from flags, environment variables and JSON files
• Hierarchical keys using struct fields
• Supports arrays, time.Duration, and most native flag types
• Auto-generated -help with usage information

Installation

go get github.com/fulldump/goconfig

Quick Start

Define your configuration struct with descriptive tags:

type myconfig struct {
        Name      string `usage:"The name of something"`
        EnableLog bool   `usage:"Enable logging into logdb" json:"enable_log"`
        MaxProcs  int    `usage:"Maximum number of procs"`
        UsersDB   db
        LogDB     db
}

type db struct {
        Host string `usage:"Host where db is located"`
        User string `usage:"Database user"`
        Pass string `usage:"Database password"`
}

Provide defaults and read the configuration:

c := &myconfig{
        EnableLog: true,
        UsersDB: db{
                Host: "localhost",
                User: "root",
                Pass: "123456",
        },
}

goconfig.Read(c)

Running your program with -help prints automatically generated help text:

Usage of example:
  -enablelog
        Enable logging into logdb [env ENABLELOG] (default true)
  -logdb.host string
        Host where db is located [env LOGDB_HOST] (default "localhost")
  -logdb.pass string
        Database password [env LOGDB_PASS] (default "123456")
  -logdb.user string
        Database user [env LOGDB_USER] (default "root")
  -maxprocs int
        Maximum number of procs [env MAXPROCS]
  -name string
        The name of something [env NAME]
  -usersdb.host string
        Host where db is located [env USERSDB_HOST]
  -usersdb.pass string
        Database password [env USERSDB_PASS]
  -usersdb.user string
        Database user [env USERSDB_USER]

Supported Types

goconfig supports the basic types from the flag package plus arrays and nested structs:

• bool
• float64
• int64
• int
• string
• uint64
• uint
• struct (hierarchical keys)
• array (any type)

The time.Duration type is fully supported and can be provided as a duration string (e.g. "15s") or as nanoseconds.

Built-in Flags

-help

Uses the standard flag behaviour to display help.

-config

Read configuration from a JSON file. Given the previous configuration structure, a sample config.json looks like:

{
  "name": "Fulanito",
  "usersdb": {
    "host": "localhost",
    "user": "admin",
    "pass": "123"
  }
}

If the -config flag is not provided, Goconfig will look for a file named config.json in the current working directory and load it if present.

Configuration precedence (highest to lowest):

1. Command line arguments
2. Environment variables
3. JSON config file
4. Default values

Contributing

Contributions are welcome! Feel free to fork the repository, submit pull requests, or open an issue if you encounter problems or have suggestions.

Testing

Run the full test suite with:

make

Example Project

This repository includes a small example. Build it with:

make example

License

Goconfig is released under the MIT License.