status-im/status-go

package bigint

import (
    "fmt"
    "math/big"
    "strings"
)

type BigInt struct {
    *big.Int
}

func (b BigInt) MarshalJSON() ([]byte, error) {
    return []byte("\"" + b.String() + "\""), nil
}

func (b *BigInt) UnmarshalJSON(p []byte) error {
    if string(p) == "null" {
        return nil
    }
    z := new(big.Int)
    _, ok := z.SetString(strings.Trim(string(p), "\""), 10)
    if !ok {
        return fmt.Errorf("not a valid big integer: %s", string(p))
    }
    b.Int = z
    return nil
}