The Go Runtime

Overview

Your Cloud Run 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 Run functions execution environment.

Select your runtime

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

gcloud functions deploy FUNCTION_NAME --no-gen2 --runtime go121 FLAGS...

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 Run functions, see the Quickstart.

Source code structure

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

Specifying dependencies

Cloud Run 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 Cloud Run functions code shows an example of context access by a Pub/Sub client:

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

import (
	"context"
	"fmt"
	"log"

	"github.com/GoogleCloudPlatform/functions-framework-go/functions"
	"github.com/cloudevents/sdk-go/v2/event"
)

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

// MessagePublishedData contains the full Pub/Sub message
// See the documentation for more details:
// https://cloud.google.com/eventarc/docs/cloudevents#pubsub
type MessagePublishedData struct {
	Message PubSubMessage
}

// PubSubMessage is the payload of a Pub/Sub event.
// See the documentation for more details:
// https://cloud.google.com/pubsub/docs/reference/rest/v1/PubsubMessage
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
}