Go go-ethereum watch ERC-20 token transfer events

erc20.go

// Code generated - DO NOT EDIT.
// This file is a generated binding and any manual changes will be lost.

package token

import (
	"math/big"
	"strings"

	ethereum "github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/accounts/abi"
	"github.com/ethereum/go-ethereum/accounts/abi/bind"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/event"
)

// TokenABI is the input ABI used to generate the binding from.
const TokenABI = "[{\"constant\":true,\"inputs\":[],\"name\":\"name\",\"outputs\":[{\"name\":\"\",\"type\":\"string\"}],\"payable\":false,\"type\":\"function\"},{\"constant\":false,\"inputs\":[{\"name\":\"_spender\",\"type\":\"address\"},{\"name\":\"_value\",\"type\":\"uint256\"}],\"name\":\"approve\",\"outputs\":[{\"name\":\"\",\"type\":\"bool\"}],\"payable\":false,\"type\":\"function\"},{\"constant\":true,\"inputs\":[],\"name\":\"totalSupply\",\"outputs\":[{\"name\":\"\",\"type\":\"uint256\"}],\"payable\":false,\"type\":\"function\"},{\"constant\":false,\"inputs\":[{\"name\":\"_from\",\"type\":\"address\"},{\"name\":\"_to\",\"type\":\"address\"},{\"name\":\"_value\",\"type\":\"uint256\"}],\"name\":\"transferFrom\",\"outputs\":[{\"name\":\"\",\"type\":\"bool\"}],\"payable\":false,\"type\":\"function\"},{\"constant\":true,\"inputs\":[],\"name\":\"decimals\",\"outputs\":[{\"name\":\"\",\"type\":\"uint8\"}],\"payable\":false,\"type\":\"function\"},{\"constant\":true,\"inputs\":[{\"name\":\"_owner\",\"type\":\"address\"}],\"name\":\"balanceOf\",\"outputs\":[{\"name\":\"\",\"type\":\"uint256\"}],\"payable\":false,\"type\":\"function\"},{\"constant\":true,\"inputs\":[],\"name\":\"symbol\",\"outputs\":[{\"name\":\"\",\"type\":\"string\"}],\"payable\":false,\"type\":\"function\"},{\"constant\":false,\"inputs\":[{\"name\":\"_to\",\"type\":\"address\"},{\"name\":\"_value\",\"type\":\"uint256\"}],\"name\":\"transfer\",\"outputs\":[{\"name\":\"\",\"type\":\"bool\"}],\"payable\":false,\"type\":\"function\"},{\"constant\":true,\"inputs\":[{\"name\":\"_owner\",\"type\":\"address\"},{\"name\":\"_spender\",\"type\":\"address\"}],\"name\":\"allowance\",\"outputs\":[{\"name\":\"\",\"type\":\"uint256\"}],\"payable\":false,\"type\":\"function\"},{\"inputs\":[],\"payable\":false,\"type\":\"constructor\"},{\"anonymous\":false,\"inputs\":[{\"indexed\":true,\"name\":\"_from\",\"type\":\"address\"},{\"indexed\":true,\"name\":\"_to\",\"type\":\"address\"},{\"indexed\":false,\"name\":\"_value\",\"type\":\"uint256\"}],\"name\":\"Transfer\",\"type\":\"event\"},{\"anonymous\":false,\"inputs\":[{\"indexed\":true,\"name\":\"_owner\",\"type\":\"address\"},{\"indexed\":true,\"name\":\"_spender\",\"type\":\"address\"},{\"indexed\":false,\"name\":\"_value\",\"type\":\"uint256\"}],\"name\":\"Approval\",\"type\":\"event\"}]"

// Token is an auto generated Go binding around an Ethereum contract.
type Token struct {
	TokenCaller     // Read-only binding to the contract
	TokenTransactor // Write-only binding to the contract
	TokenFilterer   // Log filterer for contract events
}

// TokenCaller is an auto generated read-only Go binding around an Ethereum contract.
type TokenCaller struct {
	contract *bind.BoundContract // Generic contract wrapper for the low level calls
}

// TokenTransactor is an auto generated write-only Go binding around an Ethereum contract.
type TokenTransactor struct {
	contract *bind.BoundContract // Generic contract wrapper for the low level calls
}

// TokenFilterer is an auto generated log filtering Go binding around an Ethereum contract events.
type TokenFilterer struct {
	contract *bind.BoundContract // Generic contract wrapper for the low level calls
}

// TokenSession is an auto generated Go binding around an Ethereum contract,
// with pre-set call and transact options.
type TokenSession struct {
	Contract     *Token            // Generic contract binding to set the session for
	CallOpts     bind.CallOpts     // Call options to use throughout this session
	TransactOpts bind.TransactOpts // Transaction auth options to use throughout this session
}

// TokenCallerSession is an auto generated read-only Go binding around an Ethereum contract,
// with pre-set call options.
type TokenCallerSession struct {
	Contract *TokenCaller  // Generic contract caller binding to set the session for
	CallOpts bind.CallOpts // Call options to use throughout this session
}

// TokenTransactorSession is an auto generated write-only Go binding around an Ethereum contract,
// with pre-set transact options.
type TokenTransactorSession struct {
	Contract     *TokenTransactor  // Generic contract transactor binding to set the session for
	TransactOpts bind.TransactOpts // Transaction auth options to use throughout this session
}

// TokenRaw is an auto generated low-level Go binding around an Ethereum contract.
type TokenRaw struct {
	Contract *Token // Generic contract binding to access the raw methods on
}

// TokenCallerRaw is an auto generated low-level read-only Go binding around an Ethereum contract.
type TokenCallerRaw struct {
	Contract *TokenCaller // Generic read-only contract binding to access the raw methods on
}

// TokenTransactorRaw is an auto generated low-level write-only Go binding around an Ethereum contract.
type TokenTransactorRaw struct {
	Contract *TokenTransactor // Generic write-only contract binding to access the raw methods on
}

// NewToken creates a new instance of Token, bound to a specific deployed contract.
func NewToken(address common.Address, backend bind.ContractBackend) (*Token, error) {
	contract, err := bindToken(address, backend, backend, backend)
	if err != nil {
		return nil, err
	}
	return &Token{TokenCaller: TokenCaller{contract: contract}, TokenTransactor: TokenTransactor{contract: contract}, TokenFilterer: TokenFilterer{contract: contract}}, nil
}

// NewTokenCaller creates a new read-only instance of Token, bound to a specific deployed contract.
func NewTokenCaller(address common.Address, caller bind.ContractCaller) (*TokenCaller, error) {
	contract, err := bindToken(address, caller, nil, nil)
	if err != nil {
		return nil, err
	}
	return &TokenCaller{contract: contract}, nil
}

// NewTokenTransactor creates a new write-only instance of Token, bound to a specific deployed contract.
func NewTokenTransactor(address common.Address, transactor bind.ContractTransactor) (*TokenTransactor, error) {
	contract, err := bindToken(address, nil, transactor, nil)
	if err != nil {
		return nil, err
	}
	return &TokenTransactor{contract: contract}, nil
}

// NewTokenFilterer creates a new log filterer instance of Token, bound to a specific deployed contract.
func NewTokenFilterer(address common.Address, filterer bind.ContractFilterer) (*TokenFilterer, error) {
	contract, err := bindToken(address, nil, nil, filterer)
	if err != nil {
		return nil, err
	}
	return &TokenFilterer{contract: contract}, nil
}

// bindToken binds a generic wrapper to an already deployed contract.
func bindToken(address common.Address, caller bind.ContractCaller, transactor bind.ContractTransactor, filterer bind.ContractFilterer) (*bind.BoundContract, error) {
	parsed, err := abi.JSON(strings.NewReader(TokenABI))
	if err != nil {
		return nil, err
	}
	return bind.NewBoundContract(address, parsed, caller, transactor, filterer), nil
}

// Call invokes the (constant) contract method with params as input values and
// sets the output to result. The result type might be a single field for simple
// returns, a slice of interfaces for anonymous returns and a struct for named
// returns.
func (_Token *TokenRaw) Call(opts *bind.CallOpts, result interface{}, method string, params ...interface{}) error {
	return _Token.Contract.TokenCaller.contract.Call(opts, result, method, params...)
}

// Transfer initiates a plain transaction to move funds to the contract, calling
// its default method if one is available.
func (_Token *TokenRaw) Transfer(opts *bind.TransactOpts) (*types.Transaction, error) {
	return _Token.Contract.TokenTransactor.contract.Transfer(opts)
}

// Transact invokes the (paid) contract method with params as input values.
func (_Token *TokenRaw) Transact(opts *bind.TransactOpts, method string, params ...interface{}) (*types.Transaction, error) {
	return _Token.Contract.TokenTransactor.contract.Transact(opts, method, params...)
}

// Call invokes the (constant) contract method with params as input values and
// sets the output to result. The result type might be a single field for simple
// returns, a slice of interfaces for anonymous returns and a struct for named
// returns.
func (_Token *TokenCallerRaw) Call(opts *bind.CallOpts, result interface{}, method string, params ...interface{}) error {
	return _Token.Contract.contract.Call(opts, result, method, params...)
}

// Transfer initiates a plain transaction to move funds to the contract, calling
// its default method if one is available.
func (_Token *TokenTransactorRaw) Transfer(opts *bind.TransactOpts) (*types.Transaction, error) {
	return _Token.Contract.contract.Transfer(opts)
}

// Transact invokes the (paid) contract method with params as input values.
func (_Token *TokenTransactorRaw) Transact(opts *bind.TransactOpts, method string, params ...interface{}) (*types.Transaction, error) {
	return _Token.Contract.contract.Transact(opts, method, params...)
}

// Allowance is a free data retrieval call binding the contract method 0xdd62ed3e.
//
// Solidity: function allowance(_owner address, _spender address) constant returns(uint256)
func (_Token *TokenCaller) Allowance(opts *bind.CallOpts, _owner common.Address, _spender common.Address) (*big.Int, error) {
	var (
		ret0 = new(*big.Int)
	)
	out := ret0
	err := _Token.contract.Call(opts, out, "allowance", _owner, _spender)
	return *ret0, err
}

// Allowance is a free data retrieval call binding the contract method 0xdd62ed3e.
//
// Solidity: function allowance(_owner address, _spender address) constant returns(uint256)
func (_Token *TokenSession) Allowance(_owner common.Address, _spender common.Address) (*big.Int, error) {
	return _Token.Contract.Allowance(&_Token.CallOpts, _owner, _spender)
}

// Allowance is a free data retrieval call binding the contract method 0xdd62ed3e.
//
// Solidity: function allowance(_owner address, _spender address) constant returns(uint256)
func (_Token *TokenCallerSession) Allowance(_owner common.Address, _spender common.Address) (*big.Int, error) {
	return _Token.Contract.Allowance(&_Token.CallOpts, _owner, _spender)
}

// BalanceOf is a free data retrieval call binding the contract method 0x70a08231.
//
// Solidity: function balanceOf(_owner address) constant returns(uint256)
func (_Token *TokenCaller) BalanceOf(opts *bind.CallOpts, _owner common.Address) (*big.Int, error) {
	var (
		ret0 = new(*big.Int)
	)
	out := ret0
	err := _Token.contract.Call(opts, out, "balanceOf", _owner)
	return *ret0, err
}

// BalanceOf is a free data retrieval call binding the contract method 0x70a08231.
//
// Solidity: function balanceOf(_owner address) constant returns(uint256)
func (_Token *TokenSession) BalanceOf(_owner common.Address) (*big.Int, error) {
	return _Token.Contract.BalanceOf(&_Token.CallOpts, _owner)
}

// BalanceOf is a free data retrieval call binding the contract method 0x70a08231.
//
// Solidity: function balanceOf(_owner address) constant returns(uint256)
func (_Token *TokenCallerSession) BalanceOf(_owner common.Address) (*big.Int, error) {
	return _Token.Contract.BalanceOf(&_Token.CallOpts, _owner)
}

// Decimals is a free data retrieval call binding the contract method 0x313ce567.
//
// Solidity: function decimals() constant returns(uint8)
func (_Token *TokenCaller) Decimals(opts *bind.CallOpts) (uint8, error) {
	var (
		ret0 = new(uint8)
	)
	out := ret0
	err := _Token.contract.Call(opts, out, "decimals")
	return *ret0, err
}

// Decimals is a free data retrieval call binding the contract method 0x313ce567.
//
// Solidity: function decimals() constant returns(uint8)
func (_Token *TokenSession) Decimals() (uint8, error) {
	return _Token.Contract.Decimals(&_Token.CallOpts)
}

// Decimals is a free data retrieval call binding the contract method 0x313ce567.
//
// Solidity: function decimals() constant returns(uint8)
func (_Token *TokenCallerSession) Decimals() (uint8, error) {
	return _Token.Contract.Decimals(&_Token.CallOpts)
}

// Name is a free data retrieval call binding the contract method 0x06fdde03.
//
// Solidity: function name() constant returns(string)
func (_Token *TokenCaller) Name(opts *bind.CallOpts) (string, error) {
	var (
		ret0 = new(string)
	)
	out := ret0
	err := _Token.contract.Call(opts, out, "name")
	return *ret0, err
}

// Name is a free data retrieval call binding the contract method 0x06fdde03.
//
// Solidity: function name() constant returns(string)
func (_Token *TokenSession) Name() (string, error) {
	return _Token.Contract.Name(&_Token.CallOpts)
}

// Name is a free data retrieval call binding the contract method 0x06fdde03.
//
// Solidity: function name() constant returns(string)
func (_Token *TokenCallerSession) Name() (string, error) {
	return _Token.Contract.Name(&_Token.CallOpts)
}

// Symbol is a free data retrieval call binding the contract method 0x95d89b41.
//
// Solidity: function symbol() constant returns(string)
func (_Token *TokenCaller) Symbol(opts *bind.CallOpts) (string, error) {
	var (
		ret0 = new(string)
	)
	out := ret0
	err := _Token.contract.Call(opts, out, "symbol")
	return *ret0, err
}

// Symbol is a free data retrieval call binding the contract method 0x95d89b41.
//
// Solidity: function symbol() constant returns(string)
func (_Token *TokenSession) Symbol() (string, error) {
	return _Token.Contract.Symbol(&_Token.CallOpts)
}

// Symbol is a free data retrieval call binding the contract method 0x95d89b41.
//
// Solidity: function symbol() constant returns(string)
func (_Token *TokenCallerSession) Symbol() (string, error) {
	return _Token.Contract.Symbol(&_Token.CallOpts)
}

// TotalSupply is a free data retrieval call binding the contract method 0x18160ddd.
//
// Solidity: function totalSupply() constant returns(uint256)
func (_Token *TokenCaller) TotalSupply(opts *bind.CallOpts) (*big.Int, error) {
	var (
		ret0 = new(*big.Int)
	)
	out := ret0
	err := _Token.contract.Call(opts, out, "totalSupply")
	return *ret0, err
}

// TotalSupply is a free data retrieval call binding the contract method 0x18160ddd.
//
// Solidity: function totalSupply() constant returns(uint256)
func (_Token *TokenSession) TotalSupply() (*big.Int, error) {
	return _Token.Contract.TotalSupply(&_Token.CallOpts)
}

// TotalSupply is a free data retrieval call binding the contract method 0x18160ddd.
//
// Solidity: function totalSupply() constant returns(uint256)
func (_Token *TokenCallerSession) TotalSupply() (*big.Int, error) {
	return _Token.Contract.TotalSupply(&_Token.CallOpts)
}

// Approve is a paid mutator transaction binding the contract method 0x095ea7b3.
//
// Solidity: function approve(_spender address, _value uint256) returns(bool)
func (_Token *TokenTransactor) Approve(opts *bind.TransactOpts, _spender common.Address, _value *big.Int) (*types.Transaction, error) {
	return _Token.contract.Transact(opts, "approve", _spender, _value)
}

// Approve is a paid mutator transaction binding the contract method 0x095ea7b3.
//
// Solidity: function approve(_spender address, _value uint256) returns(bool)
func (_Token *TokenSession) Approve(_spender common.Address, _value *big.Int) (*types.Transaction, error) {
	return _Token.Contract.Approve(&_Token.TransactOpts, _spender, _value)
}

// Approve is a paid mutator transaction binding the contract method 0x095ea7b3.
//
// Solidity: function approve(_spender address, _value uint256) returns(bool)
func (_Token *TokenTransactorSession) Approve(_spender common.Address, _value *big.Int) (*types.Transaction, error) {
	return _Token.Contract.Approve(&_Token.TransactOpts, _spender, _value)
}

// Transfer is a paid mutator transaction binding the contract method 0xa9059cbb.
//
// Solidity: function transfer(_to address, _value uint256) returns(bool)
func (_Token *TokenTransactor) Transfer(opts *bind.TransactOpts, _to common.Address, _value *big.Int) (*types.Transaction, error) {
	return _Token.contract.Transact(opts, "transfer", _to, _value)
}

// Transfer is a paid mutator transaction binding the contract method 0xa9059cbb.
//
// Solidity: function transfer(_to address, _value uint256) returns(bool)
func (_Token *TokenSession) Transfer(_to common.Address, _value *big.Int) (*types.Transaction, error) {
	return _Token.Contract.Transfer(&_Token.TransactOpts, _to, _value)
}

// Transfer is a paid mutator transaction binding the contract method 0xa9059cbb.
//
// Solidity: function transfer(_to address, _value uint256) returns(bool)
func (_Token *TokenTransactorSession) Transfer(_to common.Address, _value *big.Int) (*types.Transaction, error) {
	return _Token.Contract.Transfer(&_Token.TransactOpts, _to, _value)
}

// TransferFrom is a paid mutator transaction binding the contract method 0x23b872dd.
//
// Solidity: function transferFrom(_from address, _to address, _value uint256) returns(bool)
func (_Token *TokenTransactor) TransferFrom(opts *bind.TransactOpts, _from common.Address, _to common.Address, _value *big.Int) (*types.Transaction, error) {
	return _Token.contract.Transact(opts, "transferFrom", _from, _to, _value)
}

// TransferFrom is a paid mutator transaction binding the contract method 0x23b872dd.
//
// Solidity: function transferFrom(_from address, _to address, _value uint256) returns(bool)
func (_Token *TokenSession) TransferFrom(_from common.Address, _to common.Address, _value *big.Int) (*types.Transaction, error) {
	return _Token.Contract.TransferFrom(&_Token.TransactOpts, _from, _to, _value)
}

// TransferFrom is a paid mutator transaction binding the contract method 0x23b872dd.
//
// Solidity: function transferFrom(_from address, _to address, _value uint256) returns(bool)
func (_Token *TokenTransactorSession) TransferFrom(_from common.Address, _to common.Address, _value *big.Int) (*types.Transaction, error) {
	return _Token.Contract.TransferFrom(&_Token.TransactOpts, _from, _to, _value)
}

// TokenApprovalIterator is returned from FilterApproval and is used to iterate over the raw logs and unpacked data for Approval events raised by the Token contract.
type TokenApprovalIterator struct {
	Event *TokenApproval // Event containing the contract specifics and raw log

	contract *bind.BoundContract // Generic contract to use for unpacking event data
	event    string              // Event name to use for unpacking event data

	logs chan types.Log        // Log channel receiving the found contract events
	sub  ethereum.Subscription // Subscription for errors, completion and termination
	done bool                  // Whether the subscription completed delivering logs
	fail error                 // Occurred error to stop iteration
}

// Next advances the iterator to the subsequent event, returning whether there
// are any more events found. In case of a retrieval or parsing error, false is
// returned and Error() can be queried for the exact failure.
func (it *TokenApprovalIterator) Next() bool {
	// If the iterator failed, stop iterating
	if it.fail != nil {
		return false
	}
	// If the iterator completed, deliver directly whatever's available
	if it.done {
		select {
		case log := <-it.logs:
			it.Event = new(TokenApproval)
			if err := it.contract.UnpackLog(it.Event, it.event, log); err != nil {
				it.fail = err
				return false
			}
			it.Event.Raw = log
			return true

		default:
			return false
		}
	}
	// Iterator still in progress, wait for either a data or an error event
	select {
	case log := <-it.logs:
		it.Event = new(TokenApproval)
		if err := it.contract.UnpackLog(it.Event, it.event, log); err != nil {
			it.fail = err
			return false
		}
		it.Event.Raw = log
		return true

	case err := <-it.sub.Err():
		it.done = true
		it.fail = err
		return it.Next()
	}
}

// Error returns any retrieval or parsing error occurred during filtering.
func (it *TokenApprovalIterator) Error() error {
	return it.fail
}

// Close terminates the iteration process, releasing any pending underlying
// resources.
func (it *TokenApprovalIterator) Close() error {
	it.sub.Unsubscribe()
	return nil
}

// TokenApproval represents a Approval event raised by the Token contract.
type TokenApproval struct {
	Owner   common.Address
	Spender common.Address
	Value   *big.Int
	Raw     types.Log // Blockchain specific contextual infos
}

// FilterApproval is a free log retrieval operation binding the contract event 0x8c5be1e5ebec7d5bd14f71427d1e84f3dd0314c0f7b2291e5b200ac8c7c3b925.
//
// Solidity: event Approval(_owner indexed address, _spender indexed address, _value uint256)
func (_Token *TokenFilterer) FilterApproval(opts *bind.FilterOpts, _owner []common.Address, _spender []common.Address) (*TokenApprovalIterator, error) {

	var _ownerRule []interface{}
	for _, _ownerItem := range _owner {
		_ownerRule = append(_ownerRule, _ownerItem)
	}
	var _spenderRule []interface{}
	for _, _spenderItem := range _spender {
		_spenderRule = append(_spenderRule, _spenderItem)
	}

	logs, sub, err := _Token.contract.FilterLogs(opts, "Approval", _ownerRule, _spenderRule)
	if err != nil {
		return nil, err
	}
	return &TokenApprovalIterator{contract: _Token.contract, event: "Approval", logs: logs, sub: sub}, nil
}

// WatchApproval is a free log subscription operation binding the contract event 0x8c5be1e5ebec7d5bd14f71427d1e84f3dd0314c0f7b2291e5b200ac8c7c3b925.
//
// Solidity: event Approval(_owner indexed address, _spender indexed address, _value uint256)
func (_Token *TokenFilterer) WatchApproval(opts *bind.WatchOpts, sink chan<- *TokenApproval, _owner []common.Address, _spender []common.Address) (event.Subscription, error) {

	var _ownerRule []interface{}
	for _, _ownerItem := range _owner {
		_ownerRule = append(_ownerRule, _ownerItem)
	}
	var _spenderRule []interface{}
	for _, _spenderItem := range _spender {
		_spenderRule = append(_spenderRule, _spenderItem)
	}

	logs, sub, err := _Token.contract.WatchLogs(opts, "Approval", _ownerRule, _spenderRule)
	if err != nil {
		return nil, err
	}
	return event.NewSubscription(func(quit <-chan struct{}) error {
		defer sub.Unsubscribe()
		for {
			select {
			case log := <-logs:
				// New log arrived, parse the event and forward to the user
				event := new(TokenApproval)
				if err := _Token.contract.UnpackLog(event, "Approval", log); err != nil {
					return err
				}
				event.Raw = log

				select {
				case sink <- event:
				case err := <-sub.Err():
					return err
				case <-quit:
					return nil
				}
			case err := <-sub.Err():
				return err
			case <-quit:
				return nil
			}
		}
	}), nil
}

// TokenTransferIterator is returned from FilterTransfer and is used to iterate over the raw logs and unpacked data for Transfer events raised by the Token contract.
type TokenTransferIterator struct {
	Event *TokenTransfer // Event containing the contract specifics and raw log

	contract *bind.BoundContract // Generic contract to use for unpacking event data
	event    string              // Event name to use for unpacking event data

	logs chan types.Log        // Log channel receiving the found contract events
	sub  ethereum.Subscription // Subscription for errors, completion and termination
	done bool                  // Whether the subscription completed delivering logs
	fail error                 // Occurred error to stop iteration
}

// Next advances the iterator to the subsequent event, returning whether there
// are any more events found. In case of a retrieval or parsing error, false is
// returned and Error() can be queried for the exact failure.
func (it *TokenTransferIterator) Next() bool {
	// If the iterator failed, stop iterating
	if it.fail != nil {
		return false
	}
	// If the iterator completed, deliver directly whatever's available
	if it.done {
		select {
		case log := <-it.logs:
			it.Event = new(TokenTransfer)
			if err := it.contract.UnpackLog(it.Event, it.event, log); err != nil {
				it.fail = err
				return false
			}
			it.Event.Raw = log
			return true

		default:
			return false
		}
	}
	// Iterator still in progress, wait for either a data or an error event
	select {
	case log := <-it.logs:
		it.Event = new(TokenTransfer)
		if err := it.contract.UnpackLog(it.Event, it.event, log); err != nil {
			it.fail = err
			return false
		}
		it.Event.Raw = log
		return true

	case err := <-it.sub.Err():
		it.done = true
		it.fail = err
		return it.Next()
	}
}

// Error returns any retrieval or parsing error occurred during filtering.
func (it *TokenTransferIterator) Error() error {
	return it.fail
}

// Close terminates the iteration process, releasing any pending underlying
// resources.
func (it *TokenTransferIterator) Close() error {
	it.sub.Unsubscribe()
	return nil
}

// TokenTransfer represents a Transfer event raised by the Token contract.
type TokenTransfer struct {
	From  common.Address
	To    common.Address
	Value *big.Int
	Raw   types.Log // Blockchain specific contextual infos
}

// FilterTransfer is a free log retrieval operation binding the contract event 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef.
//
// Solidity: event Transfer(_from indexed address, _to indexed address, _value uint256)
func (_Token *TokenFilterer) FilterTransfer(opts *bind.FilterOpts, _from []common.Address, _to []common.Address) (*TokenTransferIterator, error) {

	var _fromRule []interface{}
	for _, _fromItem := range _from {
		_fromRule = append(_fromRule, _fromItem)
	}
	var _toRule []interface{}
	for _, _toItem := range _to {
		_toRule = append(_toRule, _toItem)
	}

	logs, sub, err := _Token.contract.FilterLogs(opts, "Transfer", _fromRule, _toRule)
	if err != nil {
		return nil, err
	}
	return &TokenTransferIterator{contract: _Token.contract, event: "Transfer", logs: logs, sub: sub}, nil
}

// WatchTransfer is a free log subscription operation binding the contract event 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef.
//
// Solidity: event Transfer(_from indexed address, _to indexed address, _value uint256)
func (_Token *TokenFilterer) WatchTransfer(opts *bind.WatchOpts, sink chan<- *TokenTransfer, _from []common.Address, _to []common.Address) (event.Subscription, error) {

	var _fromRule []interface{}
	for _, _fromItem := range _from {
		_fromRule = append(_fromRule, _fromItem)
	}
	var _toRule []interface{}
	for _, _toItem := range _to {
		_toRule = append(_toRule, _toItem)
	}

	logs, sub, err := _Token.contract.WatchLogs(opts, "Transfer", _fromRule, _toRule)
	if err != nil {
		return nil, err
	}
	return event.NewSubscription(func(quit <-chan struct{}) error {
		defer sub.Unsubscribe()
		for {
			select {
			case log := <-logs:
				// New log arrived, parse the event and forward to the user
				event := new(TokenTransfer)
				if err := _Token.contract.UnpackLog(event, "Transfer", log); err != nil {
					return err
				}
				event.Raw = log

				select {
				case sink <- event:
				case err := <-sub.Err():
					return err
				case <-quit:
					return nil
				}
			case err := <-sub.Err():
				return err
			case <-quit:
				return nil
			}
		}
	}), nil
} 

watcher.go

package watcher

import (
	"context"
	"math/big"
	"strings"
	"time"

	token "github.com/mycompany/myapp/pkg/erc20"
	ethereum "github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/accounts/abi"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/ethclient"
	"github.com/shopspring/decimal"
	log "github.com/sirupsen/logrus"
)

// Do not modify
var erc20TransferEventHash = common.HexToHash("0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef")

// WatchOnChainTransactionsInput struct
type WatchOnChainTransactionsInput struct {
	FromAddress   string
	ToAddress     string
	OutputChannel chan *WatchOnChainTransactionsOutput
}

// WatchOnChainTransactionsOutput struct
type WatchOnChainTransactionsOutput struct {
	FromAddress string
	ToAddress   string
	Amount      decimal.Decimal
	TxHash      string
}

// Service service
type Service struct {
	client *ethclient.Client
}

// NewInput input for constructor
type NewInput struct {
	ProviderURL string
}

func init() {
	log.SetLevel(log.DebugLevel)
}

// New returns new service
func New(input *NewInput) *Service {
	client, err := ethclient.Dial(input.ProviderURL)
	if err != nil {
		log.Fatal(err)
	}

	return &Service{
		client: client,
	}
}

// WatchOnChainTransactions watch for on-chain transactions
func (s *Service) WatchOnChainTransactions(input *WatchOnChainTransactionsInput) error {
	erc20Abi, err := abi.JSON(strings.NewReader(string(token.TokenABI)))
	if err != nil {
		return err
	}

	go func() {
		ticker := time.NewTicker(2 * time.Second)
		currentBlockNumber := big.NewInt(0)
		lastBlockNumberScanned := big.NewInt(0)
		for {
			select {
			case <-ticker.C:
				header, err := s.client.HeaderByNumber(context.Background(), nil)
				if err != nil {
					log.Errorf("error HeaderByNumber: %s", err)
					continue
				}

				// if block number is the same then just continue
				if header.Number.Cmp(currentBlockNumber) == 0 {
					continue
				}

				// start a little behind to make sure we didn't miss any txs
				currentBlockNumber = new(big.Int).Sub(header.Number, big.NewInt(2))
				if lastBlockNumberScanned.Cmp(currentBlockNumber) == 0 {
					continue
				}

				log.Debugf("scanning block: %v", currentBlockNumber)
				lastBlockNumberScanned = currentBlockNumber
				query := ethereum.FilterQuery{
					FromBlock: currentBlockNumber,
					ToBlock:   nil,
					Addresses: []common.Address{}, // all addresses
					Topics: [][]common.Hash{
						[]common.Hash{erc20TransferEventHash},                      // must be transfer event hash
						[]common.Hash{},                                            // must be empty
						[]common.Hash{common.HexToAddress(input.ToAddress).Hash()}, // token receiver
					},
				}

				logs, err := s.client.FilterLogs(context.Background(), query)
				if err != nil {
					log.Errorf("error getting FilterLogs: %s", err)
					continue
				}

				for _, vLog := range logs {
					output := &WatchOnChainTransactionsOutput{}
					var event = struct {
						Value *big.Int // must named "Value", dont' change.
					}{}
					err = erc20Abi.Unpack(&event, "Transfer", vLog.Data)
					if err != nil {
						log.Errorf("Subscription unpacking error: %s", err)
						continue
					}

					output.Amount = decimal.NewFromBigInt(event.Value, 0)
					output.FromAddress = common.BytesToAddress(vLog.Topics[1].Bytes()).String()
					output.ToAddress = common.BytesToAddress(vLog.Topics[2].Bytes()).String()
					output.TxHash = vLog.TxHash.String()
					input.OutputChannel <- output
				}
			}
		}
	}()

	return nil
} 

watcher_test.go

package watcher

import (
	"math/big"
	"testing"

	token "github.com/mycompany/myapp/pkg/erc20"
	"github.com/ethereum/go-ethereum/accounts/abi/bind"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/ethclient"
	"github.com/shopspring/decimal"
	log "github.com/sirupsen/logrus"
)

func decimalsToWei(amount decimal.Decimal, decimals int) *big.Int {
	mul := decimal.NewFromFloat(float64(10)).Pow(decimal.NewFromFloat(float64(decimals)))
	result := amount.Mul(mul)

	wei := new(big.Int)
	wei.SetString(result.String(), 10)

	return wei
}

func sendTokens() {
	client, err := ethclient.Dial("https://rinkeby.infura.io:443")
	if err != nil {
		log.Fatal(err)
	}

	// rinkeby
	amount := decimalsToWei(decimal.NewFromFloat(1), int(18)) // send 1 tokens
	priv := "a1ea7b205141b739070598cbc7f152cc49f69dfc6ee3cc98363dcd5ae696cbbf"
	key, err := crypto.HexToECDSA(priv)
	if err != nil {
		log.Fatal(err)
	}
	auth := *bind.NewKeyedTransactor(key)
	auth.GasLimit = uint64(350000)          // units
	auth.GasPrice = big.NewInt(40000000000) // wei (40 gwei)
	auth.Value = big.NewInt(0)
	auth.Nonce = nil // must be nil

	tokenAddress := common.HexToAddress("0x265712b02d982dca0ec2488aba707d06c1128baf")
	toAddress := common.HexToAddress("0x54282fcD78070ff03e20c56786fE46eaF4c48884")
	instance, err := token.NewToken(tokenAddress, client)
	if err != nil {
		log.Fatal(err)
	}

	tx, err := instance.Transfer(&auth, toAddress, amount)
	if err != nil {
		log.Fatal(err)
	}

	if err != nil {
		log.Fatal(err)
	}

	log.Printf("tx: %s", tx.Hash().Hex())
}

func TestWatcher(t *testing.T) {
	t.Parallel()

	sendTokens()

	s := New(&NewInput{
		ProviderURL: "https://rinkeby.infura.io:443",
	})

	outputChannel := make(chan *WatchOnChainTransactionsOutput)

	err := s.WatchOnChainTransactions(&WatchOnChainTransactionsInput{
		ToAddress:     "0x54282fcD78070ff03e20c56786fE46eaF4c48884",
		OutputChannel: outputChannel,
	})

	if err != nil {
		t.Fatal(err)
	}

	output := <-outputChannel

	log.Println(output)
}