code: func (g *Cloud) ListZonesInRegion(region string) ([]*compute.Zone, error) {
  	ctx, cancel := cloud.ContextWithCallTimeout()
  	defer cancel()
  
  	mc := newZonesMetricContext("list", region)
  	list, err := g.c.Zones().List(ctx, filter.Regexp("region", g.getRegionLink(region)))
  	if err != nil {
  		return nil, mc.Observe(err)
  	}
  	return list, mc.Observe(err)
  }
docs: // ListZonesInRegion returns all zones in a GCP region