Allow port to be changed using MTT_PORT environment variable.

src/main.rs

@@ -1,9 +1,26 @@
+use config::Config;
 use tide::{http::StatusCode, Request, Response};
 
 #[async_std::main]
 async fn main() -> tide::Result<()> {
+    let settings = Config::builder()
+        .set_default("address", "127.0.0.1")?
+        .set_default("port", "9090")?
+        .add_source(
+            config::Environment::with_prefix("MTT")
+                .try_parsing(true)
+                .separator("_")
+                .list_separator(" "),
+        )
+        .build()
+        .unwrap();
     let app = app_setup().await;
-    app.listen("127.0.0.1:9090").await?;
+    app.listen(format!(
+        "{}:{}",
+        settings.get_string("address").unwrap(),
+        settings.get_string("port").unwrap()
+    ))
+    .await?;
     Ok(())
 }