make .env file optional

for easier containerization the .env file should be optional

src/main.rs

@@ -1,6 +1,6 @@
 use actix_web::{App, HttpServer, web::Data};
 use dotenvy::dotenv;
-use tracing::Level;
+use tracing::{Level, debug};
 use tracing_subscriber::FmtSubscriber;
 
 mod access;
@@ -15,7 +15,10 @@ async fn main() -> std::io::Result<()> {
 
     tracing::subscriber::set_global_default(subscriber).expect("Could not initialize logging.");
 
-    dotenv().expect("Could not load .env file.");
+    let dr = dotenv();
+    if let Err(e) = dr {
+        debug!("Could not load .env file: {}", e);
+    }
 
     let config = config::load_config();
 
@@ -28,7 +31,9 @@ async fn main() -> std::io::Result<()> {
                 .service(handlers::get_cache_item)
                 .service(handlers::put_cache_item)
         }
-    });
+    })
+    .keep_alive(None); // disable HTTP keep-alive because it seems to break NX (at least in version 20.8)
+
     for bind_address in config.bind_addresses.unwrap_or(vec!["::0".to_string()]) {
         server = server
             .bind((bind_address.clone(), 8080))