You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: create_template_from_instance.go
    path of file: ./repos/golang-samples/compute/instance-templates/create-instance-templates
    
    the code of the file until where you have to start completion: // Copyright 2021 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package snippets

// [START compute_template_create_f
    
func createTemplateFromInstance(w io.Writer, projectID, instance, templateName string) error {
	// projectID := "your_project_id"
	// instance := "projects/project/zones/zone/instances/instance"
	// templateName := "your_template_name"

	ctx := context.Background()
	instanceTemplatesClient, err := compute.NewInstanceTemplatesRESTClient(ctx)
	if err != nil {
		return fmt.Errorf("NewInstanceTemplatesRESTClient: %w", err)
	}
	defer instanceTemplatesClient.Close()

	req := &computepb.InsertInstanceTemplateRequest{
		Project: projectID,
		InstanceTemplateResource: &computepb.InstanceTemplate{
			Name:           proto.String(templateName),
			SourceInstance: proto.String(instance),
			SourceInstanceParams: &computepb.SourceInstanceParams{
				DiskConfigs: []*computepb.DiskInstantiationConfig{
					{
						// Device name must match the name of a disk attached to the instance
						// your template is based on.
						DeviceName: proto.String("disk-1"),
						// Replace the original boot disk image used in your instance with a Rocky Linux image.
						InstantiateFrom: proto.String(computepb.DiskInstantiationConfig_CUSTOM_IMAGE.String()),
						CustomImage:     proto.String("projects/rocky-linux-cloud/global/images/family/rocky-linux-8"),
						// Override the auto_delete setting.
						AutoDelete: proto.Bool(true),
					},
				},
			},
		},
	}

	op, err := instanceTemplatesClient.Insert(ctx, req)
	if err != nil {
		return fmt.Errorf("unable to create instance template: %w", err)
	}

	if err = op.Wait(ctx); err != nil {
		return fmt.Errorf("unable to wait for the operation: %w", err)
	}

	fmt.Fprintf(w, "Instance template created\n")

	return nil
}