code snippet to filter ethereum event log

filterQuery.go

package main

import (
	"github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/ethclient"
	"context"
	"fmt"
	"math/big"
	"github.com/ethereum/go-ethereum/accounts/abi"
	"strings"
	"ethereum-development-with-go-book/code/contracts_erc20"
)

func filterQuery(){
	client, err := ethclient.Dial("https://ropsten.infura.io/aikxiYGH1Yoq8PVbKNB6")
	erc20Abi, err := abi.JSON(strings.NewReader(string(token.TokenABI)))

	if err != nil{
		fmt.Println(err.Error())
	}
	query := ethereum.FilterQuery{
		FromBlock: big.NewInt(3905790),
		ToBlock:   big.NewInt(3905792),
		Addresses: []common.Address{common.HexToAddress("0x466fb2e1979de417a30836a82c1739706938776a")}, // test token contract address
		Topics: [][]common.Hash{{common.HexToHash("0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef")}}, // transfer event
	}

	logs, err := client.FilterLogs(context.Background(), query)
	if err != nil{
		fmt.Println(err.Error())
	}
	for _, log := range logs{
		var event = struct {
			Value *big.Int // must named "Value", dont' change.
		}{}
		if len(log.Data) == 0 {
			continue
		}
		err = erc20Abi.Unpack(&event, "Transfer", log.Data)

		//value, _ :=hexutil.DecodeBig(string(log.Data[:]))

		fmt.Println("txnHash:",log.TxHash.Hex())
		fmt.Println("from:",common.BytesToAddress(log.Topics[1].Bytes()).String())
		fmt.Println("to:",common.BytesToAddress(log.Topics[2].Bytes()).String())
		fmt.Println("value:", event.Value)
		fmt.Println("value1:",common.Bytes2Hex(log.Data))
		fmt.Println("value2:",new(big.Int).SetBytes(log.Data))
		// The Removed field is true if this log was reverted due to a chain reorganisation.
		fmt.Println("txn_rollback",log.Removed)
		//fmt.Println("blockTimestamp:", block.Time().Int64())
	}
}

func main(){
	filterQuery()

/*
result:
txnHash: 0x3eef03e8be9fb3db82df5a74305cf0d2fe7440f0b9dd66176f4c989da99e2772
from: 0xfCcbE6622475C791B61ffe6Ba952875e4fEB8D1C
to: 0xAc65742DadFDE13352c919f1623FBc28A1b29D9D
value: <nil>     todo: why it's nil? as per https://ropsten.etherscan.io/tx/0x3eef03e8be9fb3db82df5a74305cf0d2fe7440f0b9dd66176f4c989da99e2772#eventlog, it's should be 1e+23
value1: 00000000000000000000000000000000000000000000152d02c7e14af6800000
value2: 100000000000000000000000
txn_rollback false
*/
}