Connecting our app to PostgreSQL

In the preceding section, we managed to connect to the PostgreSQL database using the terminal. However, we now need our app to manage the reading and writing to the database for our to-do items. In this section, we will connect our application to the database running in Docker. To connect, we must build a function that establishes a connection and then returns it. It must be stressed that there is a better way to manage the database connection and configuration, which we will cover at the end of the chapter. For now, we will implement the simplest database connection to get our application running. In the src/database.rs file, we define the function with the following code:

use diesel::prelude::*;
use diesel::pg::PgConnection;
use dotenv::dotenv;
use std::env;
pub fn establish_connection() -> PgConnection {
    dotenv().ok();
    let database_url = env::var("DATABASE_URL")
    ...