geohash.go
func EncodeWithPrecision(lat, lng float64, chars uint) string {
	bits := 5 * chars
	inthash := EncodeIntWithPrecision(lat, lng, bits)
	enc := base32encoding.Encode(inthash)
	return enc[12-chars:]
}
func EncodeWithPrecision(lat, lng float64, chars uint) string {
	bits := 5 * chars
	inthash := EncodeIntWithPrecision(lat, lng, bits)
	enc := base32encoding.Encode(inthash)
	return enc[12-chars:]
}
// EncodeWithPrecision encodes the point (lat, lng) as a string geohash with
// the specified number of characters of precision (max 12).