I would like to generate raw transactions in golang without any go binding and I'm wondering if there is library to dynamically encode my argument parameter using go?


Using this resource it look like it would be a huge amount of work to dynamically encode each param manually for every type of data available.

Is there a way to do this?

Again I'm not looking for Ethereum Go bindings since i need to return the raw unsigned transaction data.

2 Answers 2


The go-ethereum package provides a common.LeftPadBytes function for left padding values for solidity. You'd use this to pad to 32 bytes which is the word size the EVM uses.

Here's a full example of how to manually construct the transaction data for transferring an ERC-20 token which should give you an good idea (from the Ethereum Development with Go book).

package main

import (


func main() {
    client, err := ethclient.Dial("https://rinkeby.infura.io")
    if err != nil {

    privateKey, err := crypto.HexToECDSA("fad9c8855b740a0b7ed4c221dbad0f33a83a49cad6b3fe8d5817ac83d38b6a19")
    if err != nil {

    publicKey := privateKey.Public()
    publicKeyECDSA, ok := publicKey.(*ecdsa.PublicKey)
    if !ok {
        log.Fatal("error casting public key to ECDSA")

    fromAddress := crypto.PubkeyToAddress(*publicKeyECDSA)
    nonce, err := client.PendingNonceAt(context.Background(), fromAddress)
    if err != nil {

    value := big.NewInt(0)      // in wei (0 eth)
    gasLimit := uint64(2000000) // in units
    gasPrice, err := client.SuggestGasPrice(context.Background())
    if err != nil {

    toAddress := common.HexToAddress("0x4592d8f8d7b001e72cb26a73e4fa1806a51ac79d")
    tokenAddress := common.HexToAddress("0x28b149020d2152179873ec60bed6bf7cd705775d")

    transferFnSignature := []byte("transfer(address,uint256)")
    hash := sha3.NewKeccak256()
    methodID := hash.Sum(nil)[:4]
    fmt.Println(hexutil.Encode(methodID)) // 0xa9059cbb

    paddedAddress := common.LeftPadBytes(toAddress.Bytes(), 32)
    fmt.Println(hexutil.Encode(paddedAddress)) // 0x0000000000000000000000004592d8f8d7b001e72cb26a73e4fa1806a51ac79d

    amount := new(big.Int)
    amount.SetString("1000000000000000000000", 10) // 1000 tokens
    paddedAmount := common.LeftPadBytes(amount.Bytes(), 32)
    fmt.Println(hexutil.Encode(paddedAmount)) // 0x00000000000000000000000000000000000000000000003635c9adc5dea00000

    var data []byte
    data = append(data, methodID...)
    data = append(data, paddedAddress...)
    data = append(data, paddedAmount...)

    tx := types.NewTransaction(nonce, tokenAddress, value, gasLimit, gasPrice, data)
    signedTx, err := types.SignTx(tx, types.HomesteadSigner{}, privateKey)
    if err != nil {

    err = client.SendTransaction(context.Background(), signedTx)
    if err != nil {

    fmt.Printf("tx sent: %s", signedTx.Hash().Hex()) // tx sent: 0xa56316b637a94c4cc0331c73ef26389d6c097506d581073f927275e7a6ece0bc

One place to start from would be NewTransaction() in transaction.go. This is part of the types package.

// NewTransaction creates a new transaction with the given properties.
func NewTransaction(nonce int64, to *Address, amount, gasLimit, gasPrice *BigInt, data []byte) *Transaction {
    return &Transaction{types.NewTransaction(uint64(nonce), to.address, amount.bigint, gasLimit.bigint, gasPrice.bigint, data)}

There are countless places in the code which have examples of how to test the function, with or without the step that performs the signing.

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