From df9a4fa7cee06ef98545a86877f7639ebb7dacea Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 2 Sep 2022 11:12:53 +0300
Subject: [PATCH 1/8] golangci: drop deprecated linters

WARN [runner] The linter 'varcheck' is deprecated (since v1.49.0) due to: The owner seems to have abandoned the linter.  Replaced by unused.
WARN [runner] The linter 'deadcode' is deprecated (since v1.49.0) due to: The owner seems to have abandoned the linter.  Replaced by unused.
WARN [runner] The linter 'structcheck' is deprecated (since v1.49.0) due to: The owner seems to have abandoned the linter.  Replaced by unused.
---
 .golangci.yml | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/.golangci.yml b/.golangci.yml
index 1c67aa665..5c3ad60e1 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -32,16 +32,13 @@ linters:
     - revive
 
     # some default golangci-lint linters
-    - deadcode
     - errcheck
     - gosimple
     - godot
     - ineffassign
     - staticcheck
-    - structcheck
     - typecheck
     - unused
-    - varcheck
 
     # extra linters
     # - exhaustive

From 3c009271f82b401a7aa670d6987a76193c7b0a37 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 2 Sep 2022 12:21:24 +0300
Subject: [PATCH 2/8] golangci: enable bodyclose checker and fix related code

It has found an issue in the oracle code, so I think it's worth doing.
---
 .golangci.yml                            | 1 +
 pkg/rpcclient/wsclient.go                | 5 ++++-
 pkg/services/oracle/network_test.go      | 2 +-
 pkg/services/oracle/request.go           | 1 +
 pkg/services/oracle/response.go          | 2 --
 pkg/services/rpcsrv/server_test.go       | 4 +++-
 pkg/services/rpcsrv/subscription_test.go | 8 ++++++--
 7 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/.golangci.yml b/.golangci.yml
index 5c3ad60e1..2fed511a0 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -42,6 +42,7 @@ linters:
 
     # extra linters
     # - exhaustive
+    - bodyclose
     - gofmt
     - whitespace
     - goimports
diff --git a/pkg/rpcclient/wsclient.go b/pkg/rpcclient/wsclient.go
index ab77f141d..d1284716b 100644
--- a/pkg/rpcclient/wsclient.go
+++ b/pkg/rpcclient/wsclient.go
@@ -90,7 +90,10 @@ var errConnClosedByUser = errors.New("connection closed by user")
 // operating on.
 func NewWS(ctx context.Context, endpoint string, opts Options) (*WSClient, error) {
 	dialer := websocket.Dialer{HandshakeTimeout: opts.DialTimeout}
-	ws, _, err := dialer.Dial(endpoint, nil)
+	ws, resp, err := dialer.Dial(endpoint, nil)
+	if resp != nil && resp.Body != nil { // Can be non-nil even with error returned.
+		defer resp.Body.Close() // Not exactly required by websocket, but let's do this for bodyclose checker.
+	}
 	if err != nil {
 		return nil, err
 	}
diff --git a/pkg/services/oracle/network_test.go b/pkg/services/oracle/network_test.go
index 37d623939..de132508a 100644
--- a/pkg/services/oracle/network_test.go
+++ b/pkg/services/oracle/network_test.go
@@ -40,7 +40,7 @@ func TestDefaultClient_RestrictedRedirectErr(t *testing.T) {
 	}
 	for _, c := range testCases {
 		t.Run(c, func(t *testing.T) {
-			_, err := cl.Get(c)
+			_, err := cl.Get(c) //nolint:bodyclose // It errors out and it's a test.
 			require.Error(t, err)
 			require.True(t, errors.Is(err, ErrRestrictedRedirect), err)
 			require.True(t, strings.Contains(err.Error(), "IP is not global unicast"), err)
diff --git a/pkg/services/oracle/request.go b/pkg/services/oracle/request.go
index 1b6ed6197..fddc9d771 100644
--- a/pkg/services/oracle/request.go
+++ b/pkg/services/oracle/request.go
@@ -138,6 +138,7 @@ func (o *Oracle) processRequest(priv *keys.PrivateKey, req request) error {
 				o.Log.Warn("oracle request failed", zap.String("url", req.Req.URL), zap.Error(err), zap.Stringer("code", resp.Code))
 				break
 			}
+			defer r.Body.Close()
 			switch r.StatusCode {
 			case http.StatusOK:
 				if !checkMediaType(r.Header.Get("Content-Type"), o.MainCfg.AllowedContentTypes) {
diff --git a/pkg/services/oracle/response.go b/pkg/services/oracle/response.go
index b57be2f3b..7d37036e0 100644
--- a/pkg/services/oracle/response.go
+++ b/pkg/services/oracle/response.go
@@ -67,8 +67,6 @@ func (o *Oracle) AddResponse(pub *keys.PublicKey, reqID uint64, txSig []byte) {
 var ErrResponseTooLarge = errors.New("too big response")
 
 func readResponse(rc gio.ReadCloser, limit int) ([]byte, error) {
-	defer rc.Close()
-
 	buf := make([]byte, limit+1)
 	n, err := gio.ReadFull(rc, buf)
 	if err == gio.ErrUnexpectedEOF && n <= limit {
diff --git a/pkg/services/rpcsrv/server_test.go b/pkg/services/rpcsrv/server_test.go
index d5a9fce4a..e0e2ee86a 100644
--- a/pkg/services/rpcsrv/server_test.go
+++ b/pkg/services/rpcsrv/server_test.go
@@ -2633,8 +2633,9 @@ func checkErrGetBatchResult(t *testing.T, body []byte, expectingFail bool) json.
 func doRPCCallOverWS(rpcCall string, url string, t *testing.T) []byte {
 	dialer := websocket.Dialer{HandshakeTimeout: time.Second}
 	url = "ws" + strings.TrimPrefix(url, "http")
-	c, _, err := dialer.Dial(url+"/ws", nil)
+	c, r, err := dialer.Dial(url+"/ws", nil)
 	require.NoError(t, err)
+	defer r.Body.Close()
 	err = c.SetWriteDeadline(time.Now().Add(time.Second))
 	require.NoError(t, err)
 	require.NoError(t, c.WriteMessage(1, []byte(rpcCall)))
@@ -2651,6 +2652,7 @@ func doRPCCallOverHTTP(rpcCall string, url string, t *testing.T) []byte {
 	resp, err := cl.Post(url, "application/json", strings.NewReader(rpcCall))
 	require.NoErrorf(t, err, "could not make a POST request")
 	body, err := gio.ReadAll(resp.Body)
+	resp.Body.Close()
 	assert.NoErrorf(t, err, "could not read response from the request: %s", rpcCall)
 	return bytes.TrimSpace(body)
 }
diff --git a/pkg/services/rpcsrv/subscription_test.go b/pkg/services/rpcsrv/subscription_test.go
index 1a5e5a957..41a8191dc 100644
--- a/pkg/services/rpcsrv/subscription_test.go
+++ b/pkg/services/rpcsrv/subscription_test.go
@@ -59,8 +59,9 @@ func initCleanServerAndWSClient(t *testing.T) (*core.Blockchain, *Server, *webso
 
 	dialer := websocket.Dialer{HandshakeTimeout: time.Second}
 	url := "ws" + strings.TrimPrefix(httpSrv.URL, "http") + "/ws"
-	ws, _, err := dialer.Dial(url, nil)
+	ws, r, err := dialer.Dial(url, nil)
 	require.NoError(t, err)
+	defer r.Body.Close()
 
 	// Use buffered channel to read server's messages and then read expected
 	// responses from it.
@@ -520,7 +521,10 @@ func TestWSClientsLimit(t *testing.T) {
 	wss := make([]*websocket.Conn, maxSubscribers)
 
 	for i := 0; i < len(wss)+1; i++ {
-		ws, _, err := dialer.Dial(url, nil)
+		ws, r, err := dialer.Dial(url, nil)
+		if r != nil && r.Body != nil {
+			defer r.Body.Close()
+		}
 		if i < maxSubscribers {
 			require.NoError(t, err)
 			wss[i] = ws

From c703ac6805bbb90d7f8b6b79bdc6d294c102d26d Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 2 Sep 2022 12:25:51 +0300
Subject: [PATCH 3/8] golangci: enable contextcheck linter, fix WSClient

pkg/rpcclient/wsclient.go:93:30  contextcheck  Function `Dial` should pass the context parameter
---
 .golangci.yml             | 1 +
 pkg/rpcclient/wsclient.go | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/.golangci.yml b/.golangci.yml
index 2fed511a0..b35bc5bd3 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -43,6 +43,7 @@ linters:
     # extra linters
     # - exhaustive
     - bodyclose
+    - contextcheck
     - gofmt
     - whitespace
     - goimports
diff --git a/pkg/rpcclient/wsclient.go b/pkg/rpcclient/wsclient.go
index d1284716b..3a71d8bb9 100644
--- a/pkg/rpcclient/wsclient.go
+++ b/pkg/rpcclient/wsclient.go
@@ -90,7 +90,7 @@ var errConnClosedByUser = errors.New("connection closed by user")
 // operating on.
 func NewWS(ctx context.Context, endpoint string, opts Options) (*WSClient, error) {
 	dialer := websocket.Dialer{HandshakeTimeout: opts.DialTimeout}
-	ws, resp, err := dialer.Dial(endpoint, nil)
+	ws, resp, err := dialer.DialContext(ctx, endpoint, nil)
 	if resp != nil && resp.Body != nil { // Can be non-nil even with error returned.
 		defer resp.Body.Close() // Not exactly required by websocket, but let's do this for bodyclose checker.
 	}

From 4f3ffe7290fecf7b49c4d49ffe85011669e727cb Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 2 Sep 2022 14:29:47 +0300
Subject: [PATCH 4/8] golangci: enable errorlint and fix everything it found

---
 .golangci.yml                     |  1 +
 cli/server_test.go                |  3 ++-
 cli/wallet/wallet.go              |  2 +-
 pkg/core/blockchain.go            |  4 ++--
 pkg/core/dao/dao.go               |  6 +++---
 pkg/core/native/management.go     |  2 +-
 pkg/core/native/notary.go         |  2 +-
 pkg/core/storage/leveldb_store.go |  4 +++-
 pkg/neorpc/errors.go              |  9 +++++----
 pkg/network/message.go            |  2 +-
 pkg/network/server.go             | 12 ++++++------
 pkg/network/tcp_peer.go           |  2 +-
 pkg/services/metrics/metrics.go   |  3 ++-
 pkg/services/oracle/response.go   |  2 +-
 pkg/services/rpcsrv/server.go     |  4 ++--
 pkg/vm/cli/cli.go                 |  2 +-
 pkg/vm/stackitem/json.go          |  2 +-
 17 files changed, 34 insertions(+), 28 deletions(-)

diff --git a/.golangci.yml b/.golangci.yml
index b35bc5bd3..00ab87f67 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -44,6 +44,7 @@ linters:
     # - exhaustive
     - bodyclose
     - contextcheck
+    - errorlint
     - gofmt
     - whitespace
     - goimports
diff --git a/cli/server_test.go b/cli/server_test.go
index 56da8e262..09403c418 100644
--- a/cli/server_test.go
+++ b/cli/server_test.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"io"
 	"os"
 	"path/filepath"
@@ -110,7 +111,7 @@ func TestServerStart(t *testing.T) {
 			var line string
 			require.Eventually(t, func() bool {
 				line, err = e.Out.ReadString('\n')
-				if err != nil && err != io.EOF {
+				if err != nil && !errors.Is(err, io.EOF) {
 					t.Fatalf("unexpected error while reading CLI output: %s", err)
 				}
 				return err == nil
diff --git a/cli/wallet/wallet.go b/cli/wallet/wallet.go
index 54751fb84..09479ef71 100644
--- a/cli/wallet/wallet.go
+++ b/cli/wallet/wallet.go
@@ -947,7 +947,7 @@ func readWallet(ctx *cli.Context) (*wallet.Wallet, *string, error) {
 	if path == "-" {
 		w := &wallet.Wallet{}
 		if err := json.NewDecoder(os.Stdin).Decode(w); err != nil {
-			return nil, nil, fmt.Errorf("js %s", err)
+			return nil, nil, fmt.Errorf("js %w", err)
 		}
 		return w, nil, nil
 	}
diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 200e091e7..479f5a83d 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -1702,7 +1702,7 @@ func (bc *Blockchain) HasTransaction(hash util.Uint256) bool {
 	if bc.memPool.ContainsKey(hash) {
 		return true
 	}
-	return bc.dao.HasTransaction(hash) == dao.ErrAlreadyExists
+	return errors.Is(bc.dao.HasTransaction(hash), dao.ErrAlreadyExists)
 }
 
 // HasBlock returns true if the blockchain contains the given
@@ -1761,7 +1761,7 @@ func (bc *Blockchain) HeaderHeight() uint32 {
 // GetContractState returns contract by its script hash.
 func (bc *Blockchain) GetContractState(hash util.Uint160) *state.Contract {
 	contract, err := bc.contracts.Management.GetContract(bc.dao, hash)
-	if contract == nil && err != storage.ErrKeyNotFound {
+	if contract == nil && !errors.Is(err, storage.ErrKeyNotFound) {
 		bc.log.Warn("failed to get contract state", zap.Error(err))
 	}
 	return contract
diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index b9f8ced9d..5e1f17960 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -176,7 +176,7 @@ func (dao *Simple) GetTokenTransferInfo(acc util.Uint160) (*state.TokenTransferI
 	key := dao.makeTTIKey(acc)
 	bs := state.NewTokenTransferInfo()
 	err := dao.GetAndDecode(bs, key)
-	if err != nil && err != storage.ErrKeyNotFound {
+	if err != nil && !errors.Is(err, storage.ErrKeyNotFound) {
 		return nil, err
 	}
 	return bs, nil
@@ -257,7 +257,7 @@ func (dao *Simple) GetTokenTransferLog(acc util.Uint160, newestTimestamp uint64,
 	key := dao.getTokenTransferLogKey(acc, newestTimestamp, index, isNEP11)
 	value, err := dao.Store.Get(key)
 	if err != nil {
-		if err == storage.ErrKeyNotFound {
+		if errors.Is(err, storage.ErrKeyNotFound) {
 			return new(state.TokenTransferLog), nil
 		}
 		return nil, err
@@ -306,7 +306,7 @@ func (dao *Simple) GetAppExecResults(hash util.Uint256, trig trigger.Type) ([]st
 			aer := new(state.AppExecResult)
 			aer.DecodeBinary(r)
 			if r.Err != nil {
-				if r.Err == iocore.EOF {
+				if errors.Is(r.Err, iocore.EOF) {
 					break
 				}
 				return nil, r.Err
diff --git a/pkg/core/native/management.go b/pkg/core/native/management.go
index 26bd855f8..c305001d2 100644
--- a/pkg/core/native/management.go
+++ b/pkg/core/native/management.go
@@ -173,7 +173,7 @@ func (m *Management) getContract(ic *interop.Context, args []stackitem.Item) sta
 	hash := toHash160(args[0])
 	ctr, err := m.GetContract(ic.DAO, hash)
 	if err != nil {
-		if err == storage.ErrKeyNotFound {
+		if errors.Is(err, storage.ErrKeyNotFound) {
 			return stackitem.Null{}
 		}
 		panic(err)
diff --git a/pkg/core/native/notary.go b/pkg/core/native/notary.go
index 6943fbf4c..93f2af788 100644
--- a/pkg/core/native/notary.go
+++ b/pkg/core/native/notary.go
@@ -469,7 +469,7 @@ func (n *Notary) GetDepositFor(dao *dao.Simple, acc util.Uint160) *state.Deposit
 	if err == nil {
 		return deposit
 	}
-	if err == storage.ErrKeyNotFound {
+	if errors.Is(err, storage.ErrKeyNotFound) {
 		return nil
 	}
 	panic(fmt.Errorf("failed to get deposit for %s from storage: %w", acc.StringBE(), err))
diff --git a/pkg/core/storage/leveldb_store.go b/pkg/core/storage/leveldb_store.go
index c656f58bb..f1f4930f2 100644
--- a/pkg/core/storage/leveldb_store.go
+++ b/pkg/core/storage/leveldb_store.go
@@ -1,6 +1,8 @@
 package storage
 
 import (
+	"errors"
+
 	"github.com/nspcc-dev/neo-go/pkg/core/storage/dbconfig"
 	"github.com/syndtr/goleveldb/leveldb"
 	"github.com/syndtr/goleveldb/leveldb/filter"
@@ -35,7 +37,7 @@ func NewLevelDBStore(cfg dbconfig.LevelDBOptions) (*LevelDBStore, error) {
 // Get implements the Store interface.
 func (s *LevelDBStore) Get(key []byte) ([]byte, error) {
 	value, err := s.db.Get(key, nil)
-	if err == leveldb.ErrNotFound {
+	if errors.Is(err, leveldb.ErrNotFound) {
 		err = ErrKeyNotFound
 	}
 	return value, err
diff --git a/pkg/neorpc/errors.go b/pkg/neorpc/errors.go
index cc42af56e..7ed90994c 100644
--- a/pkg/neorpc/errors.go
+++ b/pkg/neorpc/errors.go
@@ -1,6 +1,7 @@
 package neorpc
 
 import (
+	"errors"
 	"fmt"
 )
 
@@ -125,9 +126,9 @@ func (e *Error) Error() string {
 
 // Is denotes whether the error matches the target one.
 func (e *Error) Is(target error) bool {
-	clTarget, ok := target.(*Error)
-	if !ok {
-		return false
+	var clTarget *Error
+	if errors.As(target, &clTarget) {
+		return e.Code == clTarget.Code
 	}
-	return e.Code == clTarget.Code
+	return false
 }
diff --git a/pkg/network/message.go b/pkg/network/message.go
index 4655c3be5..2142d6a41 100644
--- a/pkg/network/message.go
+++ b/pkg/network/message.go
@@ -176,7 +176,7 @@ func (m *Message) decodePayload() error {
 	}
 	r := io.NewBinReaderFromBuf(buf)
 	p.DecodeBinary(r)
-	if r.Err == nil || r.Err == payload.ErrTooManyHeaders {
+	if r.Err == nil || errors.Is(r.Err, payload.ErrTooManyHeaders) {
 		m.Payload = p
 	}
 
diff --git a/pkg/network/server.go b/pkg/network/server.go
index 5392071e7..cbcc40634 100644
--- a/pkg/network/server.go
+++ b/pkg/network/server.go
@@ -417,9 +417,9 @@ func (s *Server) run() {
 					zap.Error(drop.reason),
 					zap.Int("peerCount", s.PeerCount()))
 				addr := drop.peer.PeerAddr().String()
-				if drop.reason == errIdenticalID {
+				if errors.Is(drop.reason, errIdenticalID) {
 					s.discovery.RegisterBadAddr(addr)
-				} else if drop.reason == errAlreadyConnected {
+				} else if errors.Is(drop.reason, errAlreadyConnected) {
 					// There is a race condition when peer can be disconnected twice for the this reason
 					// which can lead to no connections to peer at all. Here we check for such a possibility.
 					stillConnected := false
@@ -1380,15 +1380,15 @@ func (s *Server) iteratePeersWithSendMsg(msg *Message, send func(Peer, bool, []b
 				continue
 			}
 			err := send(peer, blocking, pkt)
-			switch err {
-			case nil:
+			if err == nil {
 				if msg.Command == CMDGetAddr {
 					peer.AddGetAddrSent()
 				}
 				sentN++
-			case errBusy: // Can be retried.
+			} else if errors.Is(err, errBusy) {
+				// Can be retried.
 				continue
-			default:
+			} else {
 				deadN++
 			}
 			finished[i] = true
diff --git a/pkg/network/tcp_peer.go b/pkg/network/tcp_peer.go
index e6016a72f..e7684f156 100644
--- a/pkg/network/tcp_peer.go
+++ b/pkg/network/tcp_peer.go
@@ -170,7 +170,7 @@ func (p *TCPPeer) handleConn() {
 			msg := &Message{StateRootInHeader: p.server.config.StateRootInHeader}
 			err = msg.Decode(r)
 
-			if err == payload.ErrTooManyHeaders {
+			if errors.Is(err, payload.ErrTooManyHeaders) {
 				p.server.log.Warn("not all headers were processed")
 				r.Err = nil
 			} else if err != nil {
diff --git a/pkg/services/metrics/metrics.go b/pkg/services/metrics/metrics.go
index e204cbe32..b7af0c3a9 100644
--- a/pkg/services/metrics/metrics.go
+++ b/pkg/services/metrics/metrics.go
@@ -2,6 +2,7 @@ package metrics
 
 import (
 	"context"
+	"errors"
 	"net/http"
 
 	"github.com/nspcc-dev/neo-go/pkg/config"
@@ -21,7 +22,7 @@ func (ms *Service) Start() {
 	if ms.config.Enabled {
 		ms.log.Info("service is running", zap.String("endpoint", ms.Addr))
 		err := ms.ListenAndServe()
-		if err != nil && err != http.ErrServerClosed {
+		if err != nil && !errors.Is(err, http.ErrServerClosed) {
 			ms.log.Warn("service couldn't start on configured port")
 		}
 	} else {
diff --git a/pkg/services/oracle/response.go b/pkg/services/oracle/response.go
index 7d37036e0..d8523b2b2 100644
--- a/pkg/services/oracle/response.go
+++ b/pkg/services/oracle/response.go
@@ -69,7 +69,7 @@ var ErrResponseTooLarge = errors.New("too big response")
 func readResponse(rc gio.ReadCloser, limit int) ([]byte, error) {
 	buf := make([]byte, limit+1)
 	n, err := gio.ReadFull(rc, buf)
-	if err == gio.ErrUnexpectedEOF && n <= limit {
+	if errors.Is(err, gio.ErrUnexpectedEOF) && n <= limit {
 		return buf[:n], nil
 	}
 	if err == nil || n > limit {
diff --git a/pkg/services/rpcsrv/server.go b/pkg/services/rpcsrv/server.go
index c984293f9..1b88b561b 100644
--- a/pkg/services/rpcsrv/server.go
+++ b/pkg/services/rpcsrv/server.go
@@ -340,7 +340,7 @@ func (s *Server) Start() {
 			}
 			s.https.Addr = ln.Addr().String()
 			err = s.https.ServeTLS(ln, cfg.CertFile, cfg.KeyFile)
-			if err != http.ErrServerClosed {
+			if !errors.Is(err, http.ErrServerClosed) {
 				s.log.Error("failed to start TLS RPC server", zap.Error(err))
 				s.errChan <- err
 			}
@@ -354,7 +354,7 @@ func (s *Server) Start() {
 	s.Addr = ln.Addr().String() // set Addr to the actual address
 	go func() {
 		err = s.Serve(ln)
-		if err != http.ErrServerClosed {
+		if !errors.Is(err, http.ErrServerClosed) {
 			s.log.Error("failed to start RPC server", zap.Error(err))
 			s.errChan <- err
 		}
diff --git a/pkg/vm/cli/cli.go b/pkg/vm/cli/cli.go
index c538d8937..ae848670a 100644
--- a/pkg/vm/cli/cli.go
+++ b/pkg/vm/cli/cli.go
@@ -678,7 +678,7 @@ func (c *VMCLI) Run() error {
 	l := getReadlineInstanceFromContext(c.shell)
 	for {
 		line, err := l.Readline()
-		if err == io.EOF || err == readline.ErrInterrupt {
+		if errors.Is(err, io.EOF) || errors.Is(err, readline.ErrInterrupt) {
 			return nil // OK, stop execution.
 		}
 		if err != nil {
diff --git a/pkg/vm/stackitem/json.go b/pkg/vm/stackitem/json.go
index 2a077920f..10902e62c 100644
--- a/pkg/vm/stackitem/json.go
+++ b/pkg/vm/stackitem/json.go
@@ -169,7 +169,7 @@ func FromJSON(data []byte, maxCount int) (Item, error) {
 	d.UseNumber()
 	if item, err := d.decode(); err != nil {
 		return nil, err
-	} else if _, err := d.Token(); err != gio.EOF {
+	} else if _, err := d.Token(); !errors.Is(err, gio.EOF) {
 		return nil, fmt.Errorf("%w: unexpected items", ErrInvalidValue)
 	} else {
 		return item, nil

From 63f212f4b37dd55b42ed04b91be336e8984bcfe0 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 2 Sep 2022 17:20:39 +0300
Subject: [PATCH 5/8] golangci: enable/fix misspell

---
 .golangci.yml                    | 1 +
 pkg/core/blockchain_core_test.go | 2 +-
 pkg/core/mpt/billet.go           | 2 +-
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/.golangci.yml b/.golangci.yml
index 00ab87f67..d63fe3d3e 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -46,6 +46,7 @@ linters:
     - contextcheck
     - errorlint
     - gofmt
+    - misspell
     - whitespace
     - goimports
   disable-all: true
diff --git a/pkg/core/blockchain_core_test.go b/pkg/core/blockchain_core_test.go
index a0ccae047..8ef59604e 100644
--- a/pkg/core/blockchain_core_test.go
+++ b/pkg/core/blockchain_core_test.go
@@ -77,7 +77,7 @@ func TestAddBlock(t *testing.T) {
 }
 
 func TestRemoveOldTransfers(t *testing.T) {
-	// Creating proper number of transfers/blocks takes unneccessary time, so emulate
+	// Creating proper number of transfers/blocks takes unnecessary time, so emulate
 	// some DB with stale entries.
 	bc := newTestChain(t)
 	h, err := bc.GetHeader(bc.GetHeaderHash(0))
diff --git a/pkg/core/mpt/billet.go b/pkg/core/mpt/billet.go
index 86b2abeb6..cba44afa0 100644
--- a/pkg/core/mpt/billet.go
+++ b/pkg/core/mpt/billet.go
@@ -37,7 +37,7 @@ type Billet struct {
 
 // NewBillet returns a new billet for MPT trie restoring. It accepts a MemCachedStore
 // to decouple storage errors from logic errors so that all storage errors are
-// processed during `store.Persist()` at the caller. Another benifit is
+// processed during `store.Persist()` at the caller. Another benefit is
 // that every `Put` can be considered an atomic operation.
 func NewBillet(rootHash util.Uint256, mode TrieMode, prefix storage.KeyPrefix, store *storage.MemCachedStore) *Billet {
 	return &Billet{

From 97193cf337ba9cbfee61791b0aedec03ed1ec465 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 2 Sep 2022 18:22:35 +0300
Subject: [PATCH 6/8] golangci: add predeclared linter

These can be confusing.
---
 .golangci.yml                       |  1 +
 pkg/core/blockchain.go              | 14 +++++++-------
 pkg/core/dao/dao.go                 |  6 +++---
 pkg/neorpc/result/validator_test.go |  4 ++--
 4 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/.golangci.yml b/.golangci.yml
index d63fe3d3e..4c282cb30 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -47,6 +47,7 @@ linters:
     - errorlint
     - gofmt
     - misspell
+    - predeclared
     - whitespace
     - goimports
   disable-all: true
diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 479f5a83d..1c14b7851 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -693,15 +693,15 @@ func (bc *Blockchain) Run() {
 	}
 }
 
-func (bc *Blockchain) tryRunGC(old uint32) time.Duration {
+func (bc *Blockchain) tryRunGC(oldHeight uint32) time.Duration {
 	var dur time.Duration
 
-	new := atomic.LoadUint32(&bc.persistedHeight)
-	var tgtBlock = int64(new)
+	newHeight := atomic.LoadUint32(&bc.persistedHeight)
+	var tgtBlock = int64(newHeight)
 
 	tgtBlock -= int64(bc.config.MaxTraceableBlocks)
 	if bc.config.P2PStateExchangeExtensions {
-		syncP := new / uint32(bc.config.StateSyncInterval)
+		syncP := newHeight / uint32(bc.config.StateSyncInterval)
 		syncP--
 		syncP *= uint32(bc.config.StateSyncInterval)
 		if tgtBlock > int64(syncP) {
@@ -712,9 +712,9 @@ func (bc *Blockchain) tryRunGC(old uint32) time.Duration {
 	tgtBlock /= int64(bc.config.GarbageCollectionPeriod)
 	tgtBlock *= int64(bc.config.GarbageCollectionPeriod)
 	// Count periods.
-	old /= bc.config.GarbageCollectionPeriod
-	new /= bc.config.GarbageCollectionPeriod
-	if tgtBlock > int64(bc.config.GarbageCollectionPeriod) && new != old {
+	oldHeight /= bc.config.GarbageCollectionPeriod
+	newHeight /= bc.config.GarbageCollectionPeriod
+	if tgtBlock > int64(bc.config.GarbageCollectionPeriod) && newHeight != oldHeight {
 		tgtBlock /= int64(bc.config.GarbageCollectionPeriod)
 		tgtBlock *= int64(bc.config.GarbageCollectionPeriod)
 		dur = bc.stateRoot.GC(uint32(tgtBlock), bc.store)
diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index 5e1f17960..cd8266bef 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -828,14 +828,14 @@ func (dao *Simple) StoreAsTransaction(tx *transaction.Transaction, index uint32,
 	return nil
 }
 
-func (dao *Simple) getKeyBuf(len int) []byte {
+func (dao *Simple) getKeyBuf(l int) []byte {
 	if dao.private {
 		if dao.keyBuf == nil {
 			dao.keyBuf = make([]byte, 0, 1+4+limits.MaxStorageKeyLen) // Prefix, uint32, key.
 		}
-		return dao.keyBuf[:len] // Should have enough capacity.
+		return dao.keyBuf[:l] // Should have enough capacity.
 	}
-	return make([]byte, len)
+	return make([]byte, l)
 }
 
 func (dao *Simple) getDataBuf() *io.BufBinWriter {
diff --git a/pkg/neorpc/result/validator_test.go b/pkg/neorpc/result/validator_test.go
index f7ecd4b68..a45a81523 100644
--- a/pkg/neorpc/result/validator_test.go
+++ b/pkg/neorpc/result/validator_test.go
@@ -13,8 +13,8 @@ func TestValidatorUnmarshal(t *testing.T) {
 	require.NoError(t, json.Unmarshal(old, v))
 	require.Equal(t, int64(100500), v.Votes)
 
-	new := []byte(`{"publickey":"02a7bc55fe8684e0119768d104ba30795bdcc86619e864add26156723ed185cd62","votes":42}`)
-	require.NoError(t, json.Unmarshal(new, v))
+	newV := []byte(`{"publickey":"02a7bc55fe8684e0119768d104ba30795bdcc86619e864add26156723ed185cd62","votes":42}`)
+	require.NoError(t, json.Unmarshal(newV, v))
 	require.Equal(t, int64(42), v.Votes)
 
 	bad := []byte(`{"publickey":"02a7bc55fe8684e0119768d104ba30795bdcc86619e864add26156723ed185cd62","votes":"notanumber"}`)

From 1895dfb2c1c5134dd06a13bc51fea00c69859620 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 2 Sep 2022 14:30:08 +0300
Subject: [PATCH 7/8] golangci: enable some more linters

They have not found anything and maybe we better not have them find anything
in the future. Commented ones can be useful in future, but find too many
problems at the moment.
---
 .golangci.yml | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/.golangci.yml b/.golangci.yml
index 4c282cb30..b79417f01 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -42,12 +42,22 @@ linters:
 
     # extra linters
     # - exhaustive
+    # - goconst
+    # - goerr113
+    # - gomnd
+    # - nonamedreturns
+    # - unparam
+    - bidichk
     - bodyclose
     - contextcheck
+    - decorder
+    - durationcheck
     - errorlint
+    - exportloopref
     - gofmt
     - misspell
     - predeclared
+    - reassign
     - whitespace
     - goimports
   disable-all: true

From 6c621066a77d554565a91f6c8c2a13e30b31c043 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 2 Sep 2022 18:34:55 +0300
Subject: [PATCH 8/8] circleci: update golangci-lint to current version

---
 .circleci/config.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.circleci/config.yml b/.circleci/config.yml
index d59e6f2e7..acf83b9cd 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -34,7 +34,7 @@ jobs:
       - run:
           name: go-lint
           command: |
-            curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(go env GOPATH)/bin v1.44.2
+            curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(go env GOPATH)/bin v1.49.0
             make lint
 
   test_1_17: