Quickstart for Go in the App Engine Flexible Environment

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

Before you begin

Before running and deploying this sample, take the following steps:

  1. Use the Cloud Platform Console to create a new Cloud Platform project, create an App Engine application, and enable billing:
    Go to App Engine

    When prompted, select the region where you want your App Engine application located and then enable billing.

  2. Install the following prerequisites locally:
    1. Download and install git.
    2. Download and install the Google Cloud SDK and then initialize the gcloud tool:
      Download the SDK
  3. Alternatively: You can use Google Cloud Shell, which comes with git and Cloud SDK already installed, and many other features, such as language support and code editors.

    After Google Cloud Shell is launched, you can proceed with the rest of this tutorial and execute your commands within Cloud Shell.

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 app's are run. You can generally select the region nearest to your app's users but you should consider the location of the other Cloud Platform products and services that are utilized 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:

  • us-central1
  • us-east1
  • us-east4
  • europe-west1
  • asia-northeast1
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 App Engine flexible environment. Follow these steps from a command line to download Hello World to your local machine.

Download the sample app and navigate into the app directory:

  1. Get the Hello World sample app and its dependencies:

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

  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
    

You can see the Hello World message from the sample app displayed in 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 Cloud Platform 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 and view the app at http://YOUR_PROJECT_ID.appspot.com, by running the following command:
    gcloud app browse
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 the possible next steps that you can take.

Clean up

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

  1. Cloud Platform Console で、[プロジェクト] ページに移動します。

    [プロジェクト] ページに移動する

  2. プロジェクト名の右側にある、ゴミ箱アイコンをクリックします。

What's next

Learn the whole platform

Now that you know what it's like to develop and deploy App Engine apps, you can stretch out and see the rest of Google Cloud Platform. You already have the Google Cloud SDK installed and that gives you the tools to interact with products like Google Cloud SQL, Google Cloud Storage, Google Cloud Datastore, and more. For a guided walkthrough that teaches you how to create an application that uses the entire platform, not just App Engine, check out our quickstart on creating the Bookshelf app.

Learn about the App Engine flexible environment

Here are some topics to help continue your learning about 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 application's deployment configuration:

runtime: go
env: flex

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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App Engine flexible environment for Go