func NewBigIntFromString(x string, base int) (*BigInt, bool) {
	v, success := big.NewInt(0).SetString(x, base)
	return &BigInt{v}, success
}
NewBigInt allocates and returns a new BigInt set to x.
package math
import (
	"encoding/json"
	"fmt"
	"math/big"
)
type BigInt struct {
	Value *big.Int
}
func NewBigInt(x int64) *BigInt {
	return &BigInt{big.NewInt(x)}
}