serving/helloworld-rust: respect the PORT env var (#464)

serving/samples/helloworld-rust/README.md

@@ -2,6 +2,7 @@
 
 A simple web app written in Rust that you can use for testing.
 It reads in an env variable `TARGET` and prints "Hello ${TARGET}!". If
+
 TARGET is not specified, it will use "World" as the TARGET.
 
 ## Prerequisites
@@ -48,7 +49,17 @@ following instructions recreate the source files from this folder.
     fn main() {
         pretty_env_logger::init();
 
-        let addr = ([0, 0, 0, 0], 8080).into();
+        let mut port: u16 = 8080;
+        match env::var("PORT") {
+            Ok(p) => {
+                match p.parse::<u16>() {
+                    Ok(n) => {port = n;},
+                    Err(_e) => {},
+                };
+            }
+            Err(_e) => {},
+        };
+        let addr = ([0, 0, 0, 0], port).into();
 
         let new_service = || {
             service_fn_ok(|_| {

serving/samples/helloworld-rust/src/main.rs

@@ -10,7 +10,17 @@ use std::env;
 fn main() {
     pretty_env_logger::init();
 
-    let addr = ([0, 0, 0, 0], 8080).into();
+    let mut port: u16 = 8080;
+    match env::var("PORT") {
+        Ok(p) => {
+            match p.parse::<u16>() {
+                Ok(n) => {port = n;},
+                Err(_e) => {},
+            };
+        }
+        Err(_e) => {},
+    };
+    let addr = ([0, 0, 0, 0], port).into();
 
     let new_service = || {
         service_fn_ok(|_| {