func (a *PayToWitnessV0PubKeyHashAddress) ToString(net *network.Network) string {
	str, err := xbase.WitnessEncode(net.Bech32HRPSegwit, a.witnessVersion, a.witnessProgram[:])
	if err != nil {
		return ""
	}
	return str
}
ToString -- the implementation method for xcore.Address interface.
package xcore
import (
	"github.com/keyfuse/tokucore/network"
	"github.com/keyfuse/tokucore/xbase"
)
type PayToWitnessV0PubKeyHashAddress struct {
	witnessVersion byte
	witnessProgram [20]byte
}
func NewPayToWitnessV0PubKeyHashAddress(witnessProgram []byte) Address {
	if len(witnessProgram) != 20 {
		return nil
	}
	var witness [20]byte
	copy(witness[:], witnessProgram)
	return &PayToWitnessV0PubKeyHashAddress{
		witnessVersion: 0x00,
		witnessProgram: witness,
	}
}