code: func (ps PointSet) GeoDistanceFrom(point *Point) (float64, int) {
  	dist := math.Inf(1)
  	index := 0
  
  	for i := range ps {
  		if d := ps[i].GeoDistanceFrom(point); d < dist {
  			dist = d
  			index = i
  		}
  	}
  
  	return dist, index
  }
docs: // GeoDistanceFrom returns the minimum geo distance from the point set,
  // along with the index of the point with minimum index.