Your Cloud Run function runs in an environment consisting of anoperating system version with add-on packages, language support, andtheGo Functions Frameworklibrary that supports and invokes your function. This environment is identifiedby 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 onyour local machine and upload it. To prepare your local machine for Godevelopment, seeSet 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 duringdeployment.

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

gcloud run deployFUNCTION \    --source . \    --functionFUNCTION_ENTRYPOINT \    --base-image go125

Source code structure

For Cloud Run functions to find your function's definition, yoursource code must follow a specific structure. SeeWrite Cloud Run functions for moreinformation.

Specify dependencies

Cloud Run functions in Go must provide all of their dependencieseither with Go modules and ago.mod file, or with avendor directory. Formore information, seeSpecify dependencies in Go.

Environment variables

Your Go runtime automatically sets certain environment variables for your functionto use as needed. For details, seeConfigure environment variables.

Context type

Go'scontext package defines theContexttype, which carries deadlines, cancellation signals, and other request-scopedvalues across API boundaries and between processes.

The following code shows an example of context access by aPub/Sub client:

// Package helloworld provides a set of Cloud Functions samples.packagehelloworldimport("context""fmt""log""github.com/GoogleCloudPlatform/functions-framework-go/functions""github.com/cloudevents/sdk-go/v2/event")funcinit(){functions.CloudEvent("HelloPubSub",helloPubSub)}// MessagePublishedData contains the full Pub/Sub message// See the documentation for more details:// https://cloud.google.com/eventarc/docs/cloudevents#pubsubtypeMessagePublishedDatastruct{MessagePubSubMessage}// PubSubMessage is the payload of a Pub/Sub event.// See the documentation for more details:// https://cloud.google.com/pubsub/docs/reference/rest/v1/PubsubMessagetypePubSubMessagestruct{Data[]byte`json:"data"`}// helloPubSub consumes a CloudEvent message and extracts the Pub/Sub message.funchelloPubSub(ctxcontext.Context,eevent.Event)error{varmsgMessagePublishedDataiferr:=e.DataAs(&msg);err!=nil{returnfmt.Errorf("event.DataAs: %w",err)}name:=string(msg.Message.Data)// Automatically decoded from base64.ifname==""{name="World"}log.Printf("Hello, %s!",name)returnnil}