get env vars rust

main.rs

use std::env;

const DEFAULT_PORT: u16 = 3000;
const DEFAULT_SERVER_MODE: &str = "DEV";

fn main() {
    let server_port = env::var("SERVER_PORT").unwrap_or(DEFAULT_PORT.to_string());
    let server_mode = env::var("SERVER_MODE").unwrap_or(DEFAULT_SERVER_MODE.to_string());

    println!(
        "Starting server in {} mode on port {}.",
        server_mode, server_port
    );
}