Go 1.14 is now generally available.

Go 1.12+ Runtime Environment

The Go 1.12+ runtime is the software stack responsible for installing your web service's code and its dependencies and running your service.

The Go 1.12+ runtime for App Engine in the standard environment is declared in the app.yaml file:

Go 1.12

runtime: go112

Go 1.13

runtime: go113

Go 1.14

runtime: go114

Go version

The Go 1.12+ runtime supports Go 1.12, Go 1.13, and Go 1.14, and it uses the latest stable release of the version you choose. App Engine automatically updates to new minor revisions upon app deployment, but it will not automatically update to a new major release.

For example, your application might be deployed at Go 1.13.1 and be automatically updated to version 1.13.2 at a later deployment, but it will not be automatically updated to Go 1.14.


For more information on declaring and managing dependencies, see Specifying dependencies.

Environment variables

The following environment variables are set by the runtime:

Environment variable Description
GAE_APPLICATION The ID of your App Engine application. This ID is prefixed with 'region code~' such as 'e~' for applications deployed in Europe.
GAE_DEPLOYMENT_ID The ID of the current deployment.
GAE_ENV The App Engine environment. Set to standard.
GAE_INSTANCE The ID of the instance on which your service is currently running.
GAE_MEMORY_MB The amount of memory available to the application process, in MB.
GAE_RUNTIME The runtime specified in your app.yaml file.
GAE_SERVICE The service name specified in your app.yaml file. If no service name is specified, it is set to default.
GAE_VERSION The current version label of your service.
GOOGLE_CLOUD_PROJECT The Cloud project ID associated with your application.
PORT The port that receives HTTP requests.

You can define additional environment variables in your app.yaml file, but the above values cannot be overridden.

HTTPS and forwarding proxies

App Engine terminates HTTPS connections at the load balancer and forwards requests to your application. Some applications need to determine the original request IP and protocol. The user's IP address is available in the standard X-Forwarded-For header. Applications that require this information should configure their web framework to trust the proxy.


The runtime includes a writable /tmp directory, with all other directories having read-only access. Writing to /tmp takes up system memory. For more information, see the TempDir and TempFile documentation.

Metadata server

Each instance of your application can use the App Engine metadata server to query information about the instance and your project.

You can access the metadata server through the following endpoints:

  • http://metadata
  • http://metadata.google.internal

The following table lists the endpoints where you can make HTTP requests for specific metadata:

Metadata endpoint Description
/computeMetadata/v1/project/numeric-project-id The project number assigned to your project.
/computeMetadata/v1/project/project-id The project ID assigned to your project.
/computeMetadata/v1/instance/zone The zone the instance is running in.
/computeMetadata/v1/instance/service-accounts/default/email The default service account email assigned to your project.
/computeMetadata/v1/instance/service-accounts/default/ Lists all the default service accounts for your project.
/computeMetadata/v1/instance/service-accounts/default/scopes Lists all the supported scopes for the default service accounts.
/computeMetadata/v1/instance/service-accounts/default/token Returns the auth token that can be used to authenticate your application to other Google Cloud APIs.

For example, to retrieve your project ID, send a request to http://metadata.google.internal/computeMetadata/v1/project/project-id.