The Go runtime

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

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 Set up a Go development environment.

Supported Go runtimes and base images

Select your runtime

You can select one of the supported Go runtimes for your function during deployment.

You can select a runtime version using the Google Cloud console, or the gcloud CLI. Click the tab for instructions on using the tool of your choice:

gcloud run deploy FUNCTION \
    --source . \
    --function FUNCTION_ENTRYPOINT \
    --base-image go125

Source code structure

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

Specify 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 Specify dependencies in Go.

Environment variables

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