https://ibraheem.ca/posts/rust-global-config-files

# Rust Global Configuration Files

A simple way to decode configuration files based on the current application 
environment into globally accessible variables

The code for Rust Global Configuration Files with Multiple Environments: 
https://ibraheem.ca/posts/rust-global-config-files

Cargo.toml

[package]
name = "myapp"
version = "0.1.0"
authors = ["Ibraheem Ahmed <ibrah1440@gmail.com>"]
edition = "2018"

[dependencies]
serde = { version = "1.0.116", features = ["derive"] }
serde_yaml = "0.8"
lazy_static = "1.4.0"

config.rs

// src/config.rs

use serde::Deserialize;
use std::{env, fs, io};

pub static CONFIG_DIR: &str = "config/";
pub static APP_ENV: &str = "APP_ENV";

#[derive(Debug, Deserialize, Clone)]
pub struct Config {
  database: DatabaseConfig,
}

#[derive(Debug, Deserialize, Clone)]
pub struct DatabaseConfig {
  user: String,
  password: String,
  host: String,
  port: i32,
  database: String,
}

lazy_static! {
  static ref CONFIG: Config = Config::init();
}

impl Config {
  fn init() -> Self {
    let env = Config::get_environment();
    let env = match env {
      Ok(e) => match e.as_ref() {
        "development" | "testing" | "production" => e,
        _ => String::from("development"),
      },
      Err(_) => String::from("development"),
    };

    let contents = Self::read_config_file(env.as_ref()).unwrap();
    return serde_yaml::from_str(&contents).unwrap();
  }

  pub fn get() -> Self {
    CONFIG.to_owned()
  }

  pub fn read_config_file(env: &str) -> Result<String, io::Error> {
    fs::read_to_string(format!("{}{}.yml", CONFIG_DIR, env))
  }

  pub fn get_environment() -> Result<String, env::VarError> {
    env::var(APP_ENV)
  }
}

environments.yml

# config/environments/{development, production, testing}.yml

database:
  user: ""
  password: ""
  host: "localhost"
  port: 8080
  database: "mytribe"

main.rs

// src/main.rs

mod config;
mod error;

#[macro_use]
extern crate lazy_static;

fn main() {
    let config = config::Config::get();
    println!("{:#?}", config);
    println!("{:#?}", config.get_database_url());
}