go - What is the proper style and usage of golang Context?

Question

I am new to golang and trying to get a better understanding of context.

In the below snippet, it appears to me that I've instantiated my computeService with a context. why do I have to pass it again to the .Context() function when calling Stop()?

package main

func stopTaggedMachines(ctx context.Context, svc *compute.Service, project, zone, tag string) ([]string, error) {
    var instances []string
    f := func(page *compute.InstanceList) error {
        for _, v := range page.Items {
            if v.Labels["gcp-idler-managed"] == "true" {
                result, err := svc.Instances.Stop(project, zone, v.Name).Context(ctx).Do()
                if err != nil {
                    log.Fatal(err)
                }
                fmt.Printf("[INFO] gcp-machine-idler: Instance in state %v, Stopping %v... Response: %v 
", v.Status, v.Name, result.HTTPStatusCode)
            }
        }
        return nil
    }

    call := svc.Instances.List("my-project", "us-west1-b")
    if err := call.Pages(oauth2.NoContext, f); err != nil {
        return instances, nil
    }
    return instances, nil
}

func main() {
    // Use oauth2.NoContext if there isn't a good context to pass in.
    ctx := context.Background()

    computeService, err := compute.NewService(ctx)
    if err != nil {
        log.Fatal(err)
    }
    stopTaggedMachines(ctx, computeService, "my-project", "us-west1-b", "gcp-idler-managed")
    return
}

It seems redundant to me that I pass ctx into compute.NewService(), then again into stopTaggedMachines()

Is this really the correct convention or usage of context? Why does my call to svc.Instances.Stop(project, zone, v.Name).Context(ctx).Do() need to be passed ctx yet again as a parameter?

Answer 1

Waitting for answers