change erroneous port string naming in closure

src/main.rs

@@ -5,7 +5,7 @@ use std::error::Error;
 async fn main() -> Result<(), Box<dyn Error>> {
     swabd::serve(
         env::var("SWABD_PORT")
-            .map(|tz| tz.parse::<i32>().unwrap())
+            .map(|port| port.parse::<i32>().unwrap())
             .ok(),
         env::var("SWABD_TZ").ok(),
     )