Using envvault with Haskell

Note: Please ensure that you have completed the previous steps

Prerequisites

GHC (Glasgow Haskell Compiler) installed
Stack (Haskell build tool) installed
envvault CLI tool installed
An existing Haskell project

Usage

Running Your Application

To run your Haskell application with environment variables from envvault:

$ envvault run --env=dev stack run

Caching Environment Variables

For better performance, you can cache your environment variables:

$ envvault run --env=dev -c -- stack run

Example Implementation

Here is how to set up a basic Haskell web server with envvault:

-- app/Main.hs
{-# LANGUAGE OverloadedStrings #-}

module Main where

import Web.Scotty
import System.Environment (lookupEnv)
import Data.Maybe (fromMaybe)
import Data.Text.Lazy (pack)

main :: IO ()
main = do
  -- Your environment variables are automatically loaded
  port <- fmap (read . fromMaybe "3000") (lookupEnv "PORT")
  dbUrl <- fromMaybe "" <$> lookupEnv "DB_URL"
  
  putStrLn $ "Server running at http://localhost:" ++ show port ++ "/"
  
  scotty port $ do
    get "/" $ do
      text "Hello from envvault!"

-- package.yaml
name: my-app
version: 0.1.0.0

dependencies:
- base >= 4.7 && < 5
- scotty
- text

executables:
  my-app-exe:
    main: Main.hs
    source-dirs: app
    ghc-options:
    - -threaded
    - -rtsopts
    - -with-rtsopts=-N