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: reader.go
    path of file: ./repos/terracognita/google
    
    the code of the file until where you have to start completion: package google

import (
	"context"
	"strings"

	"github.com/pkg/errors"

	"google.golang.org/api/c
    
func (r *GCPReader) getZones() ([]string, error) {
	if len(r.zones) > 0 {
		return r.zones, nil
	}
	rs := compute.NewRegionsService(r.compute)
	region, err := rs.Get(r.project, r.region).Do()
	if err != nil {
		return nil, errors.Wrapf(err, "unable to fetch information for region %s", r.region)
	}
	// zones are URL format, e.g:
	// https://www.googleapis.com/compute/v1/projects/my-project/zones/us-central1-c
	// Need to split them
	zones := make([]string, 0, len(region.Zones))
	for _, URL := range region.Zones {
		tmp := strings.Split(URL, "/")
		zones = append(zones, tmp[len(tmp)-1])
	}
	r.zones = zones
	return zones, nil
}