Golang implements smart contracts

Preface

With the development of blockchain technology, smart contracts have become one of the hot topics. As an efficient programming language, Golang has gradually been widely used in the development of smart contracts. This article will introduce how to use Golang language to implement smart contracts.

What is a smart contract?

Smart contract is a computer program that can automatically execute, manage, and verify contract terms. Smart contracts program contract rules and realize automated management of contract execution through blockchain technology. Smart contracts can not only improve the efficiency and accuracy of contract execution, but also protect the rights and interests of all parties to the contract.

Golang implements smart contracts

As an efficient programming language, Golang has the characteristics of concurrency, lightweight, static type checking, etc., and is very suitable for implementing smart contracts. The following are the steps to implement smart contracts in Golang:

1. Install the Golang environment

First you need to install the Golang environment, you can go to the official website (https://golang.org/) Download the corresponding version of the Golang installation package and install it according to the official instructions. After the installation is complete, you can check the Golang version through the command line tool, for example:

$ go version
go version go1.16.5 darwin/amd64

2. Build a smart contract development environment

Before implementing the smart contract, you need to set up the corresponding development environment environment. First, you need to install the Solidity compiler, which is used to compile Solidity code into EVM (Ethereum Virtual Machine) bytecode. The Solidity compiler can be installed through the command line tool, for example:

$ npm install -g solc

At the same time, you need to download and install the Geth client to connect to the Ethereum network. The Geth client can be downloaded from the official website (https://geth.ethereum.org/downloads/).

3. Design Smart Contract

Before developing a smart contract, you need to design the functions and rules of the contract. Here we take the basic token smart contract as an example to introduce the implementation process of the smart contract.

The token smart contract mainly implements the following functions:

• Issuance of tokens
• Transfer of tokens
• Query of token balance

The code of the contract is as follows:

pragma solidity ^0.8.0;

contract Token {
    mapping(address => uint256) private balances;
    uint256 private totalSupply;

    constructor(uint256 _totalSupply) {
        balances[msg.sender] = _totalSupply;
        totalSupply = _totalSupply;
    }

    function transfer(address _to, uint256 _value) public returns (bool success) {
        require(balances[msg.sender] >= _value, "Not enough balance");
        balances[msg.sender] -= _value;
        balances[_to] += _value;
        return true;
    }

    function balanceOf(address _owner) public view returns (uint256 balance) {
        return balances[_owner];
    }
}

4. Writing Golang client

The smart contract is just a program and needs to be used and called through the client . Golang can connect to the Ethereum network and call smart contracts through the Web3 library.

First you need to install the Web3 library, which can be installed using the following command:

$ go get -u github.com/ethereum/go-ethereum

Then, you can write the Golang client according to the following steps:

1. First connect to Ethernet Fang Network:

client, err := ethclient.Dial("http://localhost:8545")
if err != nil {
    log.Fatal(err)
}

2. Read smart contract ABI (Application Binary Interface) and bytecode:

abi, err := abi.JSON(strings.NewReader(tokenABI))
if err != nil {
    log.Fatal(err)
}
bytecode, err := hexutil.Decode(tokenBytecode)
if err != nil {
    log.Fatal(err)
}

3. Construct contract instance:

address := common.HexToAddress(contractAddress)
tokenInstance, err := NewToken(address, client)
if err != nil {
    log.Fatal(err)
}

4. Method to call the smart contract:

balance, err := tokenInstance.BalanceOf(nil, sender)
if err != nil {
    log.Fatal(err)
}

The complete Golang client code is as follows:

package main

import (
    "context"
    "encoding/hex"
    "fmt"
    "log"
    "math/big"
    "strings"

    "github.com/ethereum/go-ethereum/accounts/abi"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/common/hexutil"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/ethclient"

    "github.com/username/repo/abi"
)

func main() {
    // Set up client
    client, err := ethclient.Dial("http://localhost:8545")
    if err != nil {
        log.Fatal(err)
    }

    // Set up sender address
    privateKey, err := crypto.HexToECDSA("PRIVATE_KEY")
    if err != nil {
        log.Fatal(err)
    }
    publicKey := privateKey.Public()
    publicKeyECDSA, ok := publicKey.(*ecdsa.PublicKey)
    if !ok {
        log.Fatal("error casting public key to ECDSA")
    }
    sender := crypto.PubkeyToAddress(*publicKeyECDSA)

    // Set up contract instance
    address := common.HexToAddress(contractAddress)
    tokenInstance, err := NewToken(address, client)
    if err != nil {
        log.Fatal(err)
    }

    // Call balanceOf method
    balance, err := tokenInstance.BalanceOf(nil, sender)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(balance)
}

Note: The private key of the account needs to be replaced here and smart contract ABI and bytecode.

5. Deploying smart contracts

After writing the smart contract code and Golang client, the smart contract needs to be deployed to the Ethereum network. You can use an online IDE like Remix (https://remix.ethereum.org/) to compile Solidity code into ABI and bytecode and deploy it to the Ethereum network.

After successful deployment, the address of the smart contract needs to be updated to the Golang client, otherwise the contract methods cannot be called.

Summary

This article introduces how to use Golang language to implement smart contracts. First, you need to set up the Solidity compiler and Geth client environment, then design the functions and rules of the smart contract, write the Golang client and connect to the Ethereum network, and finally deploy the smart contract and update the contract address to realize the use of the smart contract.

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