Gracefully shut down the server on signals (#2246)

Author: gaearon

packages/react-scripts/scripts/start.js

@@ -84,6 +84,14 @@ choosePort(HOST, DEFAULT_PORT)
       console.log(chalk.cyan('Starting the development server...\n'));
       openBrowser(urls.localUrlForBrowser);
     });
+
+    ['SIGINT', 'SIGTERM'].forEach(function(sig) {
+      process.on(sig, function() {
+        console.log(`Gracefully shutting down server after ${sig}...`);
+        server.close();
+        process.exit();
+      });
+    });
   })
   .catch(err => {
     if (err && err.message) {