Quickstart for Go in the App Engine Flexible Environment

This quickstart shows you how to create a small App Engine app that displays a short message.

Before you begin

Before running and deploying this quickstart, install the Cloud SDK and then set up a GCP project for App Engine:

  1. Download and install Cloud SDK:

    Download the SDK

    Note: If you already have the Cloud SDK installed, update it by running the following command:

    gcloud components update
    
  2. Create a new project:

    gcloud projects create [YOUR_PROJECT_ID] --set-as-default
    

    Verify the project was created:

    gcloud projects describe [YOUR_PROJECT_ID]
    

    You see project details that might look like the following:

    createTime: year-month-hour
    lifecycleState: ACTIVE
    name: project-name
    parent:
    id: '433637338589'
    type: organization
    projectId: project-name-id
    projectNumber: 499227785679
    
  3. Initialize your App Engine app with your project and choose its region:

    gcloud app create --project=[YOUR_PROJECT_ID]
    

    When prompted, select the region where you want your App Engine application located.

  4. Make sure billing is enabled for your project. A billing account needs to be linked to your project in order for the application to be deployed to App Engine.

    Enable billing

    Your flexible environment deployment will incur costs while it is active. Clean up your project when you are finished to avoid ongoing costs.

  5. Install the following prerequisites:

    • Run the following command to install the gcloud component that includes the App Engine extension for Go:

      gcloud components install app-engine-go
      

App Engine locations

App Engine is regional, which means the infrastructure that runs your apps is located in a specific region and is managed by Google to be redundantly available across all the zones within that region.

Meeting your latency, availability, or durability requirements are primary factors for selecting the region where your apps are run. You can generally select the region nearest to your app's users but you should consider the location of the other GCP products and services that are used by your app. Using services across multiple locations can affect your app's latency as well as pricing.

App Engine is available in the following regions:

  • northamerica-northeast1 (Montréal)
  • us-central (Iowa)
  • us-west2 (Los Angeles)
  • us-east1 (South Carolina)
  • us-east4 (Northern Virginia)
  • southamerica-east1 (São Paulo)
  • europe-west (Belgium)
  • europe-west2 (London)
  • europe-west3 (Frankfurt)
  • europe-west6 (Zürich)
  • asia-northeast1 (Tokyo)
  • asia-northeast2 (Osaka)
  • asia-east2 (Hong Kong)
  • asia-south1 (Mumbai)
  • australia-southeast1 (Sydney)

You cannot change an app's region after you set it.

If you already created an App Engine application, you can view the region by running the gcloud app describe command or opening the App Engine Dashboard in the GCP Console. The region of your App Engine application is listed under http://[YOUR_PROJECT_ID].appspot.com.

This quickstart assumes that you are familiar with the Go programming language and that you have installed Go.

Download the Hello World app

We've created a simple Hello World app for Go so you can quickly get a feel for deploying an app to the Google Cloud Platform.

  1. Clone the Hello World sample app repository to your local machine.

    go get -u -d github.com/GoogleCloudPlatform/golang-samples/appengine_flexible
    

  2. Change to the directory that contains the sample code.

    cd $GOPATH/src/github.com/GoogleCloudPlatform/golang-samples/appengine_flexible/helloworld
    

Run Hello World on your local machine

To run the Hello World app on your local computer:

  1. Start a local web server.

    go run *.go
    
  2. In your web browser, enter the following address:

    http://localhost:8080

The Hello World message from the sample app displays on the page. In your terminal window, press Ctrl+C to exit the web server.

Deploy and run Hello World on App Engine

To deploy your app to the App Engine flexible environment:

  1. Deploy the Hello World app by running the following command from the helloworld directory:

    gcloud app deploy

    Learn about the optional flags.

    Common gcloud command flags

    • Include the --version flag to specify an ID that uniquely identifies that version of your app, otherwise one is generated for you. Example: --version [YOUR_VERSION_ID]
    • Include the --project flag to specify an alternate GCP project ID to what you initialized as the default in the gcloud tool. Example: --project [YOUR_PROJECT_ID]

    Example:

    gcloud app deploy --version pre-prod-5 --project my-sample-app

    To learn more about deploying your app from the command line, see Testing and Deploying Your App . For a list of all the command flags, see the gcloud app deploy reference.

  2. Launch your browser to view the app at http://YOUR_PROJECT_ID.appspot.com

    gcloud app browse
    where YOUR_PROJECT_ID represents your GCP project ID.

This time, the page that displays the Hello World message is delivered by a web server running on an App Engine instance.

Congratulations! You've deployed your first Go app to App Engine flexible environment!

See the following sections for information about cleaning up as well as links to possible next steps that you can take.

Clean up

To avoid incurring charges, you can delete your GCP project to stop billing for all the resources used within that project.

  1. In the GCP Console, go to the Manage resources page.

    Go to the Manage resources page

  2. In the project list, select the project you want to delete and click Delete .
  3. In the dialog, type the project ID, and then click Shut down to delete the project.

What's next

Now that you've accomplished Hello World, you can start exploring your next sample app: the Bookshelf app. The Bookshelf app is a more complete, yet still basic Go web app that uses multiple Cloud Platform features, such as data storage, authentication, logging, pub/sub, and more.

Start the Bookshelf app tutorial

For more information about the App Engine flexible environment, see An Overview Of App Engine.

Hello World code review

Hello World is the simplest possible App Engine app, as it contains only one service, has only one version, and all of the code is located within the app's root directory. This section describes each of the app files in detail.

helloworld.go

The helloworld.go file registers a handler that listens for requests to /, and responds with the 'Hello world!' message.


package main

import (
	"fmt"
	"log"
	"net/http"
)

func main() {
	http.HandleFunc("/", handle)
	http.HandleFunc("/_ah/health", healthCheckHandler)
	log.Print("Listening on port 8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
}

func handle(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/" {
		http.NotFound(w, r)
		return
	}
	fmt.Fprint(w, "Hello world!")
}

func healthCheckHandler(w http.ResponseWriter, r *http.Request) {
	fmt.Fprint(w, "ok")
}

app.yaml

The app.yaml file describes an app's deployment configuration:

# Copyright 2019 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

runtime: go
env: flex

# This sample incurs costs to run on the App Engine flexible environment.
# The settings below are to reduce costs during testing and are not appropriate
# for production use. For more information, see:
# https://cloud.google.com/appengine/docs/flexible/python/configuring-your-app-with-app-yaml
manual_scaling:
  instances: 1
resources:
  cpu: 1
  memory_gb: 0.5
  disk_size_gb: 10

Here, app.yaml specifies the runtime used by the app, and sets env: flex, specifying that the app uses the flexible environment.

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