src\settings.rs

use config::{Config, ConfigError, Environment, File};
use serde_derive::Deserialize;
use std::env;

#[derive(Deserialize)]
pub struct ServerSettings {
    pub host: String,
    pub port: i32,
}

#[derive(Deserialize)]
pub struct Settings {
    pub server: ServerSettings,
}

impl Settings {
    pub fn new() -> Result<Self, ConfigError> {
        let env = env::var("environment").unwrap_or("development".into());

        let mut cfg = Config::new();
        cfg.merge(File::with_name("settings"))?;
        cfg.merge(File::with_name(&format!("settings_{}", env)).required(false))?;
        cfg.merge(Environment::new())?;
        cfg.try_into()
    }
}