The Go Runtime


Your Cloud Function runs in an environment consisting of an operating system version plus add-on packages, language support, and the Functions Framework library that supports and invokes your function. This environment is identified by the language version, and is known as the runtime.

For information about runtimes in general, and to learn which Ubuntu version each Go runtime uses, see the Cloud Functions execution environment.

Select your runtime

Cloud Functions supports several versions of Go, listed on the Runtime support page. You can select the preferred Go runtime for your function during deployment.


If you're using the Google Cloud CLI, specify the runtime by using the --runtime parameter with the Go runtime of your choice. For example:

gcloud functions deploy FUNCTION_NAME --runtime go121 FLAGS...

FLAGS... refers to arguments passed during the first deployment of your function. For more information regarding required and optional arguments, see Deploy using the Google Cloud CLI.


If you're using the Google Cloud console, see the Google Cloud console quickstart for detailed instructions.

Function preparation

You can prepare a function directly from the Google Cloud console or write it on your local machine and upload it. To prepare your local machine for Go development, see Setting Up a Go Development Environment.

To get started quickly with Go on Cloud Functions, see the Quickstart.

Source code structure

For Cloud Functions to find your function's definition, your source code must follow a specific structure. See Writing Cloud Functions for more information.

Specifying dependencies

Cloud Functions in Go must provide all of their dependencies either with Go modules and a go.mod file, or with a vendor directory. For more information, see Specifying dependencies in Go.

Environment variables

Your Go runtime automatically sets certain environment variables for your function to use as needed. For details, see Using Environment Variables.

Context type

Go's context package defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes.

The following 2nd gen code shows an example of context access by a Pub/Sub client:

// Package helloworld provides a set of Cloud Functions samples.
package helloworld

import (


func init() {
	functions.CloudEvent("HelloPubSub", helloPubSub)

// MessagePublishedData contains the full Pub/Sub message
// See the documentation for more details:
type MessagePublishedData struct {
	Message PubSubMessage

// PubSubMessage is the payload of a Pub/Sub event.
// See the documentation for more details:
type PubSubMessage struct {
	Data []byte `json:"data"`

// helloPubSub consumes a CloudEvent message and extracts the Pub/Sub message.
func helloPubSub(ctx context.Context, e event.Event) error {
	var msg MessagePublishedData
	if err := e.DataAs(&msg); err != nil {
		return fmt.Errorf("event.DataAs: %w", err)

	name := string(msg.Message.Data) // Automatically decoded from base64.
	if name == "" {
		name = "World"
	log.Printf("Hello, %s!", name)
	return nil