go-localenvironment

Apply environment variables sourced from env.json, .env, or custom sources in the current working directory. This is a port of the coreybutler/localenvironment Node.js module.

Basic Usage

import "github.com/coreybutler/go-localenvironment"

func main() {
  localenvironment.Apply()
}

Overview

This package provides a lightweight approach to environment variable management within an application. It will look for a file called env.json or .env. If one or both files exist, each key is added as an environment variable, accessible via the os.Getenv method. If the file does not exist, it is silently ignored.

Example Usage

Consider the following directory contents:

> dir
  - env.json
  - .env
  - main.go

env.json

{
  "MY_API_KEY": "12345"
}

.env

MY_OTHER_API_KEY=ABC67890

main.go:

package main

import (
  "os"
  "log"
  "github.com/coreybutler/go-localenvironment"
)

func main() {
  err := localenvironment.Apply() // Apply the env.json/.env attributes to the environment variables.
  if err != nil {
    log.Printf("Error: %s", err)
  }

  apiKey := os.Getenv("MY_API_KEY")
  otherApiKey := os.Getenv("MY_OTHER_API_KEY")

  log.Printf("My API key is %s. The other is %s.\n", apiKey, otherApiKey)
}

Running main.go will log My API key is 12345. The other is ABC67890..

Variables applied by localenvironment are ephemerally added to the environment. They are not persisted to the user/system environment variable store. If MY_API_URL is defined as a user/system variable, it will still be available whether localenvironment applies env.json/.env variables or not.

In the case of a conflicting variable, localenvironment will override values at runtime only. For example, if MY_API_KEY=abcde is defined as a user environment variable, localenvironment will override the value of MY_API_KEY with the value from the env.json/.env file (i.e. it will be 12345).

Variable Flattening/Expansion (JSON only)

Nested JSON properties are automatically flattened.

For example:

{
  "a": {
    "b": {
      "c": "something"
    }
  }
}

The data structure above would be flattened into an environment variable called A_B_C, with a value of something.

Custom Sources (other than env.json/.env)

It is possible to specify an alternative JSON/KV files using the ApplyFile method:

package main

import (
    "os"
    "log"
    "github.com/coreybutler/go-localenvironment"
)

func main() {
    err := localenvironment.ApplyFile("/path/to/config.json") // Apply your own attributes to the environment variables.
    if err != nil {
      log.Printf("Error: %s", err)
    }

    apiKey := os.Getenv("...")
}

Multiple Sources

While less common, there are circumstances where it is useful to apply more than one configuration to the environment variables. The ApplyFiles method supports this.

package main

import (
    "os"
    "log"
    "github.com/coreybutler/go-localenvironment"
)

func main() {
    err := localenvironment.ApplyFiles(
      "/path/to/config.json",
      "/path/to/other.json"
    ) // Apply your own attributes to the environment variables.

    if err != nil {
      log.Printf("Error: %s", err)
    }

    apiKey := os.Getenv("...")
}

Why?

This is a simple approach for adding environment variable management to code. Alternatively (or in addition), it may be desirable to define environment variables in the build process. For this, QuikGo provides a robust option leveraging similar techniques.