Add Cloud Functions template render sample.

functions/helloworld/index.js

@@ -148,3 +148,15 @@ exports.helloError3 = function helloError3 (event, callback) {
 };
 // [END functions_helloworld_error_3]
 /* eslint-enable */
+
+// [START functions_helloworld_template]
+const pug = require('pug');
+
+// Renders the index.pug
+exports.helloTemplate = (req, res) => {
+  // Render the index.pug file
+  const html = pug.renderFile('./index.pug');
+
+  res.send(html).end();
+};
+// [END functions_helloworld_template]

functions/helloworld/index.pug

@@ -0,0 +1,9 @@
+doctype html
+html(lang="en")
+  head
+    title= pageTitle
+  body
+    h1 Cloud Functions Template Sample
+    p.
+      Pug is a terse and simple templating language with a
+      strong focus on performance and powerful features.

functions/helloworld/package.json

@@ -18,6 +18,7 @@
   },
   "dependencies": {
     "@google-cloud/debug-agent": "1.0.0",
+    "pug": "2.0.0-beta.12",
     "safe-buffer": "5.0.1"
   },
   "devDependencies": {

functions/helloworld/test/index.test.js

@@ -192,3 +192,17 @@ test.serial(`helloError3: callback shoud return an errback value`, (t) => {
   t.deepEqual(callback.callCount, 1);
   t.deepEqual(callback.firstCall.args, [expectedMsg]);
 });
+
+test.serial(`helloTemplate: should render the html`, async (t) => {
+  const req = {};
+  const res = {};
+  res.send = sinon.stub().returnsThis();
+  res.end = sinon.stub().returnsThis();
+
+  program.helloTemplate(req, res);
+
+  t.is(res.send.callCount, 1);
+  t.is(res.send.getCall(0).args.length, 1);
+  t.is(res.send.getCall(0).args[0].includes('<h1>Cloud Functions Template Sample</h1>'), true);
+  t.is(res.end.callCount, 1);
+});