getting-started: listen on PORT

[kemokemo]

Hi!

I'm a beginner of GCP and learning the GCP with the official tutorials.
First of all, thak you so much the very nice tutorials! 😃

Issue

I was practicing the this tutorial, but panic occurred at the frontend 'app' and it did not work. The error log that occurred at that time was confirmed with Stackdriver below.

{
    "textPayload": "panic: Metadata fetch failed for 'instance/attributes/gae_project': metadata server returned HTTP 404\n\ngoroutine 89 [running]:\ngoogle.golang.org/appengine/internal.mustGetMetadata(0xb7d3a3, 0x1f, 0x0, 0x0, 0x0)\n\t/go/src/google.golang.org/appengine/internal/metadata.go:34 +0x18a\ngoogle.golang.org/appengine/internal.partitionlessAppID(0x0, 0xc000262600)\n\t/go/src/google.golang.org/appengine/internal/identity_vm.go:112 +0xa2\ngoogle.golang.org/appengine/internal.DefaultTicket.func1()\n\t/go/src/google.golang.org/appengine/internal/api.go:293 +0x86\nsync.(*Once).Do(0x112f6c8, 0xb98848)\n\t/usr/local/go/src/sync/once.go:44 +0xb3\ngoogle.golang.org/appengine/internal.DefaultTicket(0xc0007d1dd0, 0xa117c0)\n\t/go/src/google.golang.org/appengine/internal/api.go:288 +0x39\ngoogle.golang.org/appengine/internal.Call(0xc1f0e0, 0xc0007d1dd0, 0xb6e0c3, 0xa, 0xb695e4, 0x5, 0xc1c420, 0xc000262600, 0xc1b620, 0xc00040e0e0, ...)\n\t/go/src/google.golang.org/appengine/internal/api.go:495 +0x852\ngoogle.golang.org/appengine/internal.(*context).flushLog(0xc000444900, 0xb99401, 0xc0005cc200)\n\t/go/src/google.golang.org/appengine/internal/api.go:637 +0x3d0\ngoogle.golang.org/appengine/internal.handleHTTP.func1(0xc0005cc2a0, 0xc000444900)\n\t/go/src/google.golang.org/appengine/internal/api.go:137 +0x56\ncreated by google.golang.org/appengine/internal.handleHTTP\n\t/go/src/google.golang.org/appengine/internal/api.go:133 +0x350\n",
    "insertId": "1kvvdxfg3s9go81",
    "resource": {
      "type": "container",
      "labels": {
        "cluster_name": "bookshelf",
        "container_name": "bookshelf-app",
        "namespace_id": "default",
        "instance_id": "8544645641522474976",
        "pod_id": "bookshelf-frontend-5d9f864b5c-6pjxj",
        "zone": "asia-northeast1-a",
        "project_id": "mybookshelf-226812"
      }
    },
    "timestamp": "2018-12-30T07:52:57Z",
    "severity": "ERROR",
    "labels": {
      "compute.googleapis.com/resource_name": "fluentd-gcp-v3.1.0-n497k",
      "container.googleapis.com/pod_name": "bookshelf-frontend-5d9f864b5c-6pjxj",
      "container.googleapis.com/stream": "stderr",
      "container.googleapis.com/namespace_name": "default"
    },
    "logName": "projects/mybookshelf-226812/logs/bookshelf-app",
    "receiveTimestamp": "2018-12-30T07:53:05.999226813Z"
  },

When building the same app locally and executing it did not work with the following error.

panic: Metadata fetch failed for 'instance/attributes/gae_project': Get http://metadata/computeMetadata/v1/instance/attributes/gae_project: dial tcp: lookup metadata: no such host

Changes to solve the issue

Remove the google.golang.org/appengine and apply the new runtime go111 for the App Engine.
Thank you for your review.

[googlebot]

So there's good news and bad news.

👍 The good news is that everyone that needs to sign a CLA (the pull request submitter and all commit authors) have done so. Everything is all good there.

😕 The bad news is that it appears that one or more commits were authored or co-authored by someone other than the pull request submitter. We need to confirm that all authors are ok with their commits being contributed to this project. Please have them confirm that here in the pull request.

Note to project maintainer: This is a terminal state, meaning the cla/google commit status will not change from this state. It's up to you to confirm consent of all the commit author(s), set the cla label to yes (if enabled on your project), and then merge this pull request when appropriate.

[broady]

I made one change. @tbpg for final approval + merge.

[broady]

Thanks for the contribution!

[googlebot]

A Googler has manually verified that the CLAs look good.

(Googler, please make sure the reason for overriding the CLA status is clearly documented in these comments.)

[tbpg]

Thank you! LGTM - waiting for tests.

CLA looks good - was verified before @broady (a Googler) made an update.

[kemokemo]

Thank you so much for your reviewing and fixing!
I'm proud that I contributed to this wonderful GCP sample code. 😃