└── main.go


/main.go:
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 1 | package main
 2 | 
 3 | import (
 4 | 	"context"
 5 | 	"crypto/ecdsa"
 6 | 	"fmt"
 7 | 	"log"
 8 | 	"math/big"
 9 | 
10 | 	"github.com/ethereum/go-ethereum"
11 | 	"github.com/ethereum/go-ethereum/common"
12 | 	"github.com/ethereum/go-ethereum/common/hexutil"
13 | 	"github.com/ethereum/go-ethereum/core/types"
14 | 	"github.com/ethereum/go-ethereum/crypto"
15 | 	"github.com/ethereum/go-ethereum/crypto/sha3"
16 | 	"github.com/ethereum/go-ethereum/ethclient"
17 | )
18 | 
19 | func main() {
20 | 	client, err := ethclient.Dial("http://127.0.0.1:9545")
21 | 	if err != nil {
22 | 		log.Fatal(err)
23 | 	}
24 | 
25 | 	privateKey, err := crypto.HexToECDSA("...")
26 | 	if err != nil {
27 | 		log.Fatal(err)
28 | 	}
29 | 
30 | 	publicKey := privateKey.Public()
31 | 	publicKeyECDSA, ok := publicKey.(*ecdsa.PublicKey)
32 | 	if !ok {
33 | 		log.Fatal("error casting public key to ECDSA")
34 | 	}
35 | 
36 | 	fromAddress := crypto.PubkeyToAddress(*publicKeyECDSA)
37 | 	nonce, err := client.PendingNonceAt(context.Background(), fromAddress)
38 | 	if err != nil {
39 | 		log.Fatal(err)
40 | 	}
41 | 
42 | 	value := big.NewInt(0) // in wei (0 eth)
43 | 	gasPrice, err := client.SuggestGasPrice(context.Background())
44 | 	if err != nil {
45 | 		log.Fatal(err)
46 | 	}
47 | 
48 | 	toAddress := common.HexToAddress("...")
49 | 	tokenAddress := common.HexToAddress("...")
50 | 
51 | 	transferFnSignature := []byte("transfer(address,uint256)")
52 | 	hash := sha3.NewKeccak256()
53 | 	hash.Write(transferFnSignature)
54 | 	methodID := hash.Sum(nil)[:4]
55 | 	fmt.Printf("Method ID: %s\n", hexutil.Encode(methodID))
56 | 
57 | 	paddedAddress := common.LeftPadBytes(toAddress.Bytes(), 32)
58 | 	fmt.Printf("To address: %s\n", hexutil.Encode(paddedAddress))
59 | 
60 | 	amount := new(big.Int)
61 | 	amount.SetString("1000000000000000000000", 10) // 1000 tokens
62 | 	paddedAmount := common.LeftPadBytes(amount.Bytes(), 32)
63 | 	fmt.Printf("Token amount: %s", hexutil.Encode(paddedAmount))
64 | 
65 | 	var data []byte
66 | 	data = append(data, methodID...)
67 | 	data = append(data, paddedAddress...)
68 | 	data = append(data, paddedAmount...)
69 | 
70 | 	gasLimit, err := client.EstimateGas(context.Background(), ethereum.CallMsg{
71 | 		To:   &toAddress,
72 | 		Data: data,
73 | 	})
74 | 	if err != nil {
75 | 		log.Fatal(err)
76 | 	}
77 | 	fmt.Printf("Gas limit: %d", gasLimit)
78 | 
79 | 	tx := types.NewTransaction(nonce, tokenAddress, value, gasLimit, gasPrice, data)
80 | 	signedTx, err := types.SignTx(tx, types.HomesteadSigner{}, privateKey)
81 | 	if err != nil {
82 | 		log.Fatal(err)
83 | 	}
84 | 
85 | 	err = client.SendTransaction(context.Background(), signedTx)
86 | 	if err != nil {
87 | 		log.Fatal(err)
88 | 	}
89 | 
90 | 	fmt.Printf("Tokens sent at TX: %s", signedTx.Hash().Hex())
91 | }
92 | 


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