How to interact with mainnet smart contracts by GOlang?

Question

Please tell me an example of code in GOlang that connects to the contract and checks the balance of the ERC20 token / transfer tokens / gets the name of the token. I looked for examples and did not find anything worthwhile, everything is connected to their local contract

Answer 1

you can refer this link https://goethereumbook.org/smart-contract-read-erc20

for simplicity you can also directly use the package github.com/liyue201/erc20-go/erc20 and call the balance functions like this

func getERC20Balance(address string, tokenAddress string) big.Float {
    tokenAddressHex := common.HexToAddress(tokenAddress)
    addressHex := common.HexToAddress(tokenAddress)

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

    instance, err := erc20.NewGGToken(tokenAddressHex, client)
    if err != nil {
        log.Fatal(err)
    }

    bal, err := instance.BalanceOf(nil, addressHex)
    if err != nil {
        log.Fatal(err)
    }

    name, err := instance.Name(nil)
    if err != nil {
        log.Fatal(err)
    }

    symbol, err := instance.Symbol(nil)
    if err != nil {
        log.Fatal(err)
    }

    decimals, err := instance.Decimals(nil)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Printf("name: %s\n", name)         // "name: Golem Network"
    fmt.Printf("symbol: %s\n", symbol)     // "symbol: GNT"
    fmt.Printf("decimals: %v\n", decimals) // "decimals: 18"

    fmt.Printf("wei: %s\n", bal) // "wei: 74605500647408739782407023"

    fbal := new(big.Float)
    fbal.SetString(bal.String())
    value := new(big.Float).Quo(fbal, big.NewFloat(math.Pow10(int(decimals))))

    fmt.Printf("balance: %f\n", value) // "balance: 74605500.647409"

    return *value

}

hope this helps!