Added config file for db (#9)

Reviewed-on: #9
Co-authored-by: KD <kundeng94@gmail.com>
Co-committed-by: KD <kundeng94@gmail.com>

src/lib.rs

@@ -1,3 +1,33 @@
 pub mod callers;
 pub mod config;
 pub mod models;
+
+mod keys {
+    pub const DBURL: &str = "DATABASE_URL";
+
+    pub mod error {
+        pub const ERROR: &str = "DATABASE_URL must be set in .env";
+    }
+}
+
+mod connection_settings {
+    pub const MAXCONN: u32 = 5;
+}
+
+pub mod db_pool {
+
+    use sqlx::postgres::PgPoolOptions;
+    use std::env;
+
+    use crate::{connection_settings, keys};
+
+    pub async fn create_pool() -> Result<sqlx::PgPool, sqlx::Error> {
+        dotenv::dotenv().ok();
+        let database_url = env::var(keys::DBURL).expect(keys::error::ERROR);
+
+        PgPoolOptions::new()
+            .max_connections(connection_settings::MAXCONN)
+            .connect(&database_url)
+            .await
+    }
+}