code: func ClusterGeoPointers(pointers []geo.Pointer, threshold float64) []*Cluster {
  	clusters := make([]*Cluster, 0, len(pointers))
  	for _, p := range pointers {
  		clusters = append(clusters, NewCluster(p))
  	}
  
  	if len(clusters) < 2 {
  		return clusters
  	}
  
  	// performs the actual clustering
  	return geocluster(clusters, threshold)
  }
docs: // ClusterGeoPointers will take a set of Pointers and cluster them.
  // It will project the points using mercator, scale the threshold, cluster, and project back.
  // Performace is about 40% than simply using a geo distancer.
  // This may not make sense for all geo datasets.