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package main
import (
"context"
"crypto/ecdsa"
"fmt"
"log"
"math/big"
ethereum "github.com/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/hexutil"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/ethclient"
"golang.org/x/crypto/sha3"
)
func main() {
client, err := ethclient.Dial("https://rinkeby.infura.io")
if err != nil {
log.Fatal(err)
}
privateKey, err := crypto.HexToECDSA("fad9c8855b740a0b7ed4c221dbad0f33a83a49cad6b3fe8d5817ac83d38b6a19")
if err != nil {
log.Fatal(err)
}
publicKey := privateKey.Public()
publicKeyECDSA, ok := publicKey.(*ecdsa.PublicKey)
if !ok {
log.Fatal("cannot assert type: publicKey is not of type *ecdsa.PublicKey")
}
fromAddress := crypto.PubkeyToAddress(*publicKeyECDSA)
nonce, err := client.PendingNonceAt(context.Background(), fromAddress)
if err != nil {
log.Fatal(err)
}
value := big.NewInt(0) // in wei (0 eth)
gasPrice, err := client.SuggestGasPrice(context.Background())
if err != nil {
log.Fatal(err)
}
toAddress := common.HexToAddress("0x4592d8f8d7b001e72cb26a73e4fa1806a51ac79d")
tokenAddress := common.HexToAddress("0x28b149020d2152179873ec60bed6bf7cd705775d")
transferFnSignature := []byte("transfer(address,uint256)")
hash := sha3.NewLegacyKeccak256()
hash.Write(transferFnSignature)
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) // sets the value to 1000 tokens, in the token denomination
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...)
gasLimit, err := client.EstimateGas(context.Background(), ethereum.CallMsg{
To: &tokenAddress,
Data: data,
})
if err != nil {
log.Fatal(err)
}
fmt.Println(gasLimit) // 23256
tx := types.NewTransaction(nonce, tokenAddress, value, gasLimit, gasPrice, data)
chainID, err := client.NetworkID(context.Background())
if err != nil {
log.Fatal(err)
}
signedTx, err := types.SignTx(tx, types.NewEIP155Signer(chainID), privateKey)
if err != nil {
log.Fatal(err)
}
err = client.SendTransaction(context.Background(), signedTx)
if err != nil {
log.Fatal(err)
}
fmt.Printf("tx sent: %s", signedTx.Hash().Hex()) // tx sent: 0xa56316b637a94c4cc0331c73ef26389d6c097506d581073f927275e7a6ece0bc
}
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