diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index c122a34..34d76a4 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -70,7 +70,7 @@ jobs:
       - name: Run linter
         uses: golangci/golangci-lint-action@v2
         with:
-          version: v1.37.1
+          version: v1.39.0
 
   docker:
     name: Docker
diff --git a/.golangci.toml b/.golangci.toml
index 40560ac..216d371 100644
--- a/.golangci.toml
+++ b/.golangci.toml
@@ -3,7 +3,6 @@ concurrency = 4
 deadline = "2m"
 tests = true
 skip-dirs = ["vendor"]
-skip-files = ["version.go"]
 
 [output]
 format = "colored-line-number"
diff --git a/Makefile b/Makefile
index fff4788..a786d4d 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@ APP_NAME     := $(IMAGE_NAME)
 
 CC_BINARIES  := $(shell bash -c "echo -n $(APP_NAME)-{linux,freebsd,openbsd}-{386,amd64} $(APP_NAME)-linux-{arm,arm64}")
 
-GOLANGCI_LINT_VERSION := v1.37.1
+GOLANGCI_LINT_VERSION := v1.39.0
 
 VERSION_GO         := $(shell go version)
 VERSION_DATE       := $(shell date -Ru)
diff --git a/events/event_stream_test.go b/events/event_stream_test.go
index 93152c6..6989c77 100644
--- a/events/event_stream_test.go
+++ b/events/event_stream_test.go
@@ -46,8 +46,9 @@ func (suite *EventStreamTestSuite) TestEventStart() {
 			On("EventStart", mock.Anything).
 			Once().
 			Run(func(args mock.Arguments) {
-				caught := args.Get(0).(mtglib.EventStart)
+				caught, ok := args.Get(0).(mtglib.EventStart)
 
+				suite.True(ok)
 				suite.Equal(evt.RemoteIP.String(), caught.RemoteIP.String())
 				suite.Equal(evt.StreamID(), caught.StreamID())
 				suite.Equal(evt.Timestamp(), caught.Timestamp())
@@ -66,8 +67,9 @@ func (suite *EventStreamTestSuite) TestEventConnectedToDC() {
 			On("EventConnectedToDC", mock.Anything).
 			Once().
 			Run(func(args mock.Arguments) {
-				caught := args.Get(0).(mtglib.EventConnectedToDC)
+				caught, ok := args.Get(0).(mtglib.EventConnectedToDC)
 
+				suite.True(ok)
 				suite.Equal(evt.RemoteIP.String(), caught.RemoteIP.String())
 				suite.Equal(evt.StreamID(), caught.StreamID())
 				suite.Equal(evt.DC, caught.DC)
@@ -87,8 +89,9 @@ func (suite *EventStreamTestSuite) TestEventDomainFronting() {
 			On("EventDomainFronting", mock.Anything).
 			Once().
 			Run(func(args mock.Arguments) {
-				caught := args.Get(0).(mtglib.EventDomainFronting)
+				caught, ok := args.Get(0).(mtglib.EventDomainFronting)
 
+				suite.True(ok)
 				suite.Equal(evt.StreamID(), caught.StreamID())
 				suite.Equal(evt.Timestamp(), caught.Timestamp())
 			})
@@ -106,8 +109,9 @@ func (suite *EventStreamTestSuite) TestEventTraffic() {
 			On("EventTraffic", mock.Anything).
 			Once().
 			Run(func(args mock.Arguments) {
-				caught := args.Get(0).(mtglib.EventTraffic)
+				caught, ok := args.Get(0).(mtglib.EventTraffic)
 
+				suite.True(ok)
 				suite.Equal(evt.StreamID(), caught.StreamID())
 				suite.Equal(evt.Timestamp(), caught.Timestamp())
 				suite.Equal(evt.Traffic, caught.Traffic)
@@ -127,8 +131,9 @@ func (suite *EventStreamTestSuite) TestEventFinish() {
 			On("EventFinish", mock.Anything).
 			Once().
 			Run(func(args mock.Arguments) {
-				caught := args.Get(0).(mtglib.EventFinish)
+				caught, ok := args.Get(0).(mtglib.EventFinish)
 
+				suite.True(ok)
 				suite.Equal(evt.StreamID(), caught.StreamID())
 				suite.Equal(evt.Timestamp(), caught.Timestamp())
 			})
@@ -146,8 +151,9 @@ func (suite *EventStreamTestSuite) TestEventConcurrencyLimited() {
 			On("EventConcurrencyLimited", mock.Anything).
 			Once().
 			Run(func(args mock.Arguments) {
-				caught := args.Get(0).(mtglib.EventConcurrencyLimited)
+				caught, ok := args.Get(0).(mtglib.EventConcurrencyLimited)
 
+				suite.True(ok)
 				suite.Equal(evt.Timestamp(), caught.Timestamp())
 				suite.Empty(evt.StreamID())
 			})
@@ -165,8 +171,9 @@ func (suite *EventStreamTestSuite) TestEventIPBlocklisted() {
 			On("EventIPBlocklisted", mock.Anything).
 			Once().
 			Run(func(args mock.Arguments) {
-				caught := args.Get(0).(mtglib.EventIPBlocklisted)
+				caught, ok := args.Get(0).(mtglib.EventIPBlocklisted)
 
+				suite.True(ok)
 				suite.Equal(evt.StreamID(), caught.StreamID())
 				suite.Equal(evt.Timestamp(), caught.Timestamp())
 				suite.Equal(evt.RemoteIP.String(), caught.RemoteIP.String())
@@ -185,8 +192,9 @@ func (suite *EventStreamTestSuite) TestEventReplayAttack() {
 			On("EventReplayAttack", mock.Anything).
 			Once().
 			Run(func(args mock.Arguments) {
-				caught := args.Get(0).(mtglib.EventReplayAttack)
+				caught, ok := args.Get(0).(mtglib.EventReplayAttack)
 
+				suite.True(ok)
 				suite.Equal(evt.StreamID(), caught.StreamID())
 				suite.Equal(evt.Timestamp(), caught.Timestamp())
 			})
diff --git a/go.mod b/go.mod
index b9f9f50..677750f 100644
--- a/go.mod
+++ b/go.mod
@@ -9,6 +9,7 @@ require (
 	github.com/armon/go-socks5 v0.0.0-20160902184237-e75332964ef5
 	github.com/babolivier/go-doh-client v0.0.0-20201028162107-a76cff4cb8b6
 	github.com/d4l3k/messagediff v1.2.1 // indirect
+	github.com/google/go-cmp v0.5.5 // indirect
 	github.com/jarcoal/httpmock v1.0.8
 	github.com/kentik/patricia v0.0.0-20201202224819-f9447a6e25f1
 	github.com/libp2p/go-reuseport v0.0.2
@@ -23,6 +24,7 @@ require (
 	github.com/tylertreat/BoomFilters v0.0.0-20200520150052-42a7b4300c0c
 	github.com/xeipuuv/gojsonschema v1.2.0
 	golang.org/x/crypto v0.0.0-20210322153248-0c34fe9e7dc2
-	golang.org/x/net v0.0.0-20210226172049-e18ecbb05110
-	golang.org/x/sys v0.0.0-20210309074719-68d13333faf2
+	golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4
+	golang.org/x/sys v0.0.0-20210403161142-5e06dd20ab57
+	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
 )
diff --git a/go.sum b/go.sum
index 0cf083c..b855446 100644
--- a/go.sum
+++ b/go.sum
@@ -102,8 +102,9 @@ github.com/google/btree v1.0.0/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
-github.com/google/go-cmp v0.4.0 h1:xsAVV57WRhGj6kEIi8ReJzQlHHqcBYCElAvkovg3B/4=
 github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
+github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
 github.com/google/renameio v0.1.0/go.mod h1:KWCgfxg9yswjAJkECMjeO8J8rahYeXnNhOm40UhjYkI=
 github.com/google/uuid v1.0.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
@@ -351,8 +352,9 @@ golang.org/x/net v0.0.0-20190613194153-d28f0bde5980/go.mod h1:z5CRVTTTmAJ677TzLL
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20200625001655-4c5254603344/go.mod h1:/O7V0waA8r7cgGh81Ro3o1hOxt32SMVPicZroKQ2sZA=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110 h1:qWPm9rbaAMKs8Bq/9LRpbMqxWRVUAQwMI9fVrssnTfw=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4 h1:4nGaVu0QrbjT/AK2PRLuQfQuh6DJve+pELhqTdAj3x0=
+golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4/go.mod h1:p54w0d4576C0XHj96bSt6lcn1PtDYWL6XObtHCRCNQM=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20190226205417-e64efc72b421/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
@@ -383,8 +385,9 @@ golang.org/x/sys v0.0.0-20200615200032-f1bc736245b1/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20200625212154-ddb9806d33ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201214210602-f9fddec55a1e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210309074719-68d13333faf2 h1:46ULzRKLh1CwgRq2dC5SlBzEqqNCi8rreOZnNrbqcIY=
-golang.org/x/sys v0.0.0-20210309074719-68d13333faf2/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210330210617-4fbd30eecc44/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210403161142-5e06dd20ab57 h1:F5Gozwx4I1xtr/sr/8CFbb57iKi3297KFs0QDbGN60A=
+golang.org/x/sys v0.0.0-20210403161142-5e06dd20ab57/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
@@ -407,8 +410,9 @@ golang.org/x/tools v0.0.0-20191029190741-b9c20aec41a5/go.mod h1:b+2E5dAYhXwXZwtn
 golang.org/x/tools v0.0.0-20200103221440-774c71fcf114/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
+golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/api v0.3.1/go.mod h1:6wY9I6uQWHQ8EM57III9mq/AjF+i8G65rmVagqKMtkk=
 google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
 google.golang.org/appengine v1.2.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
diff --git a/internal/cli/access.go b/internal/cli/access.go
index d443f87..57083cc 100644
--- a/internal/cli/access.go
+++ b/internal/cli/access.go
@@ -102,7 +102,7 @@ func (c *Access) Execute(cli *CLI) error {
 
 func (c *Access) getIP(protocol string) net.IP {
 	client := c.Network.MakeHTTPClient(func(ctx context.Context, network, address string) (net.Conn, error) {
-		return c.Network.DialContext(ctx, protocol, address)
+		return c.Network.DialContext(ctx, protocol, address) // nolint: wrapcheck
 	})
 
 	req, err := http.NewRequest(http.MethodGet, "https://ifconfig.co", nil) // nolint: noctx
diff --git a/internal/cli/base.go b/internal/cli/base.go
index 95c4410..0bdc93b 100644
--- a/internal/cli/base.go
+++ b/internal/cli/base.go
@@ -62,14 +62,14 @@ func (b *base) makeNetwork(conf *config.Config, version string) (mtglib.Network,
 
 	switch len(proxyURLs) {
 	case 0:
-		return network.NewNetwork(baseDialer, userAgent, dohIP, httpTimeout)
+		return network.NewNetwork(baseDialer, userAgent, dohIP, httpTimeout) // nolint: wrapcheck
 	case 1:
 		socksDialer, err := network.NewSocks5Dialer(baseDialer, proxyURLs[0])
 		if err != nil {
 			return nil, fmt.Errorf("cannot build socks5 dialer: %w", err)
 		}
 
-		return network.NewNetwork(socksDialer, userAgent, dohIP, httpTimeout)
+		return network.NewNetwork(socksDialer, userAgent, dohIP, httpTimeout) // nolint: wrapcheck
 	}
 
 	socksDialer, err := network.NewLoadBalancedSocks5Dialer(baseDialer, proxyURLs)
@@ -77,5 +77,5 @@ func (b *base) makeNetwork(conf *config.Config, version string) (mtglib.Network,
 		return nil, fmt.Errorf("cannot build socks5 dialer: %w", err)
 	}
 
-	return network.NewNetwork(socksDialer, userAgent, dohIP, httpTimeout)
+	return network.NewNetwork(socksDialer, userAgent, dohIP, httpTimeout) // nolint: wrapcheck
 }
diff --git a/internal/testlib/mtglib_network_mock.go b/internal/testlib/mtglib_network_mock.go
index 092bd28..0f58a25 100644
--- a/internal/testlib/mtglib_network_mock.go
+++ b/internal/testlib/mtglib_network_mock.go
@@ -15,13 +15,13 @@ type MtglibNetworkMock struct {
 func (m *MtglibNetworkMock) Dial(network, address string) (net.Conn, error) {
 	args := m.Called(network, address)
 
-	return args.Get(0).(net.Conn), args.Error(1)
+	return args.Get(0).(net.Conn), args.Error(1) // nolint: wrapcheck
 }
 
 func (m *MtglibNetworkMock) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
 	args := m.Called(ctx, network, address)
 
-	return args.Get(0).(net.Conn), args.Error(1)
+	return args.Get(0).(net.Conn), args.Error(1) // nolint: wrapcheck
 }
 
 func (m *MtglibNetworkMock) MakeHTTPClient(dialFunc func(ctx context.Context,
diff --git a/internal/testlib/net_conn_mock.go b/internal/testlib/net_conn_mock.go
index b2fc1a3..e167665 100644
--- a/internal/testlib/net_conn_mock.go
+++ b/internal/testlib/net_conn_mock.go
@@ -24,7 +24,7 @@ func (n *NetConnMock) Write(b []byte) (int, error) {
 }
 
 func (n *NetConnMock) Close() error {
-	return n.Called().Error(0)
+	return n.Called().Error(0) // nolint: wrapcheck
 }
 
 func (n *NetConnMock) LocalAddr() net.Addr {
@@ -36,13 +36,13 @@ func (n *NetConnMock) RemoteAddr() net.Addr {
 }
 
 func (n *NetConnMock) SetDeadline(t time.Time) error {
-	return n.Called(t).Error(0)
+	return n.Called(t).Error(0) // nolint: wrapcheck
 }
 
 func (n *NetConnMock) SetReadDeadline(t time.Time) error {
-	return n.Called(t).Error(0)
+	return n.Called(t).Error(0) // nolint: wrapcheck
 }
 
 func (n *NetConnMock) SetWriteDeadline(t time.Time) error {
-	return n.Called(t).Error(0)
+	return n.Called(t).Error(0) // nolint: wrapcheck
 }
diff --git a/ipblocklist/firehol.go b/ipblocklist/firehol.go
index 947134b..953aeba 100644
--- a/ipblocklist/firehol.go
+++ b/ipblocklist/firehol.go
@@ -68,12 +68,10 @@ func (f *Firehol) Contains(ip net.IP) bool {
 		return true
 	}
 
-	ip4 := ip.To4()
-
 	f.rwMutex.RLock()
 	defer f.rwMutex.RUnlock()
 
-	if ip4 != nil {
+	if ip4 := ip.To4(); ip4 != nil {
 		return f.containsIPv4(ip4)
 	}
 
diff --git a/mtglib/conns.go b/mtglib/conns.go
index da0b046..8dfb3a4 100644
--- a/mtglib/conns.go
+++ b/mtglib/conns.go
@@ -48,7 +48,7 @@ func (c *connRewind) Read(p []byte) (int, error) {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
 
-	return c.active.Read(p)
+	return c.active.Read(p) // nolint: wrapcheck
 }
 
 func (c *connRewind) Rewind() {
diff --git a/mtglib/conns_internal_test.go b/mtglib/conns_internal_test.go
index 0c73759..8149b0d 100644
--- a/mtglib/conns_internal_test.go
+++ b/mtglib/conns_internal_test.go
@@ -22,7 +22,7 @@ type ConnRewindBaseConn struct {
 func (c *ConnRewindBaseConn) Read(p []byte) (int, error) {
 	c.Called(p)
 
-	return c.readBuffer.Read(p)
+	return c.readBuffer.Read(p) // nolint: wrapcheck
 }
 
 type ConnTrafficTestSuite struct {
@@ -54,8 +54,9 @@ func (suite *ConnTrafficTestSuite) TestReadOk() {
 		On("Send", mock.Anything, mock.Anything).
 		Once().
 		Run(func(args mock.Arguments) {
-			evt := args.Get(1).(EventTraffic)
+			evt, ok := args.Get(1).(EventTraffic)
 
+			suite.True(ok)
 			suite.Equal("CONNID", evt.StreamID())
 			suite.WithinDuration(time.Now(), evt.Timestamp(), time.Second)
 			suite.EqualValues(10, evt.Traffic)
@@ -68,13 +69,14 @@ func (suite *ConnTrafficTestSuite) TestReadOk() {
 	suite.Equal(10, n)
 }
 
-func (suite *ConnTrafficTestSuite) TestReadErr() {
+func (suite *ConnTrafficTestSuite) TestReadErr() { // nolint: dupl
 	suite.eventStreamMock.
 		On("Send", mock.Anything, mock.Anything).
 		Once().
 		Run(func(args mock.Arguments) {
-			evt := args.Get(1).(EventTraffic)
+			evt, ok := args.Get(1).(EventTraffic)
 
+			suite.True(ok)
 			suite.Equal("CONNID", evt.StreamID())
 			suite.WithinDuration(time.Now(), evt.Timestamp(), time.Second)
 			suite.EqualValues(10, evt.Traffic)
@@ -108,8 +110,9 @@ func (suite *ConnTrafficTestSuite) TestWriteOk() {
 		On("Send", mock.Anything, mock.Anything).
 		Once().
 		Run(func(args mock.Arguments) {
-			evt := args.Get(1).(EventTraffic)
+			evt, ok := args.Get(1).(EventTraffic)
 
+			suite.True(ok)
 			suite.Equal("CONNID", evt.StreamID())
 			suite.WithinDuration(time.Now(), evt.Timestamp(), time.Second)
 			suite.EqualValues(10, evt.Traffic)
@@ -122,13 +125,14 @@ func (suite *ConnTrafficTestSuite) TestWriteOk() {
 	suite.Equal(10, n)
 }
 
-func (suite *ConnTrafficTestSuite) TestWriteErr() {
+func (suite *ConnTrafficTestSuite) TestWriteErr() { // nolint: dupl
 	suite.eventStreamMock.
 		On("Send", mock.Anything, mock.Anything).
 		Once().
 		Run(func(args mock.Arguments) {
-			evt := args.Get(1).(EventTraffic)
+			evt, ok := args.Get(1).(EventTraffic)
 
+			suite.True(ok)
 			suite.Equal("CONNID", evt.StreamID())
 			suite.WithinDuration(time.Now(), evt.Timestamp(), time.Second)
 			suite.EqualValues(10, evt.Traffic)
diff --git a/mtglib/internal/faketls/conn.go b/mtglib/internal/faketls/conn.go
index 06592ff..868563e 100644
--- a/mtglib/internal/faketls/conn.go
+++ b/mtglib/internal/faketls/conn.go
@@ -32,7 +32,7 @@ func (c *Conn) Read(p []byte) (int, error) {
 		case record.TypeApplicationData:
 			rec.Payload.WriteTo(&c.readBuffer) // nolint: errcheck
 
-			return c.readBuffer.Read(p)
+			return c.readBuffer.Read(p) // nolint: wrapcheck
 		case record.TypeChangeCipherSpec:
 		default:
 			return 0, fmt.Errorf("unsupported record type %v", rec.Type)
diff --git a/mtglib/internal/faketls/conn_test.go b/mtglib/internal/faketls/conn_test.go
index 73c0e65..affcec0 100644
--- a/mtglib/internal/faketls/conn_test.go
+++ b/mtglib/internal/faketls/conn_test.go
@@ -24,13 +24,13 @@ type ConnMock struct {
 func (m *ConnMock) Read(p []byte) (int, error) {
 	m.Called(p)
 
-	return m.readBuffer.Read(p)
+	return m.readBuffer.Read(p) // nolint: wrapcheck
 }
 
 func (m *ConnMock) Write(p []byte) (int, error) {
 	m.Called(p)
 
-	return m.writeBuffer.Write(p)
+	return m.writeBuffer.Write(p) // nolint: wrapcheck
 }
 
 type ConnTestSuite struct {
diff --git a/mtglib/internal/faketls/welcome.go b/mtglib/internal/faketls/welcome.go
index d0b48d2..0b5e5c0 100644
--- a/mtglib/internal/faketls/welcome.go
+++ b/mtglib/internal/faketls/welcome.go
@@ -45,8 +45,8 @@ func SendWelcomePacket(writer io.Writer, secret []byte, clientHello ClientHello)
 	packet := buf.Bytes()
 	mac := hmac.New(sha256.New, secret)
 
-	mac.Write(clientHello.Random[:]) // nolint: errcheck
-	mac.Write(packet)                // nolint: errcheck
+	mac.Write(clientHello.Random[:])
+	mac.Write(packet)
 
 	copy(packet[WelcomePacketRandomOffset:], mac.Sum(nil))
 
diff --git a/mtglib/internal/faketls/welcome_test.go b/mtglib/internal/faketls/welcome_test.go
index 4f1b990..33129e2 100644
--- a/mtglib/internal/faketls/welcome_test.go
+++ b/mtglib/internal/faketls/welcome_test.go
@@ -70,8 +70,8 @@ func (suite *WelcomeTestSuite) TestOk() {
 	copy(welcomePacket[11:], empty)
 
 	mac := hmac.New(sha256.New, suite.secret.Key[:])
-	mac.Write(suite.h.Random[:]) // nolint: errcheck
-	mac.Write(welcomePacket)     // nolint: errcheck
+	mac.Write(suite.h.Random[:])
+	mac.Write(welcomePacket)
 
 	suite.Equal(random, mac.Sum(nil))
 }
diff --git a/mtglib/internal/obfuscated2/client_handshake.go b/mtglib/internal/obfuscated2/client_handshake.go
index 89cc396..229cf83 100644
--- a/mtglib/internal/obfuscated2/client_handshake.go
+++ b/mtglib/internal/obfuscated2/client_handshake.go
@@ -16,8 +16,8 @@ func (c *clientHandhakeFrame) decryptor(secret []byte) cipher.Stream {
 	hasher := acquireSha256Hasher()
 	defer releaseSha256Hasher(hasher)
 
-	hasher.Write(c.key()) // nolint: errcheck
-	hasher.Write(secret)  // nolint: errcheck
+	hasher.Write(c.key())
+	hasher.Write(secret)
 
 	return makeAesCtr(hasher.Sum(nil), c.iv())
 }
@@ -28,8 +28,8 @@ func (c *clientHandhakeFrame) encryptor(secret []byte) cipher.Stream {
 	hasher := acquireSha256Hasher()
 	defer releaseSha256Hasher(hasher)
 
-	hasher.Write(invertedHandshake.key()) // nolint: errcheck
-	hasher.Write(secret)                  // nolint: errcheck
+	hasher.Write(invertedHandshake.key())
+	hasher.Write(secret)
 
 	return makeAesCtr(hasher.Sum(nil), invertedHandshake.iv())
 }
diff --git a/mtglib/internal/obfuscated2/client_handshake_test.go b/mtglib/internal/obfuscated2/client_handshake_test.go
index 6d4b95a..6d4d8c2 100644
--- a/mtglib/internal/obfuscated2/client_handshake_test.go
+++ b/mtglib/internal/obfuscated2/client_handshake_test.go
@@ -47,14 +47,18 @@ func (suite *ClientHandshakeTestSuite) TestOk() {
 				Once().
 				Return(len(snapshot.Decrypted.Text.data), nil).
 				Run(func(args mock.Arguments) {
-					arr := args.Get(0).([]byte)
+					arr, ok := args.Get(0).([]byte)
+
+					suite.True(ok)
 					copy(arr, snapshot.Decrypted.Cipher.data)
 				})
 			connMock.On("Write", mock.Anything).
 				Once().
 				Return(len(snapshot.Encrypted.Text.data), nil).
 				Run(func(args mock.Arguments) {
-					arr := args.Get(0).([]byte)
+					arr, ok := args.Get(0).([]byte)
+
+					suite.True(ok)
 					copy(writeData, arr)
 				})
 
diff --git a/mtglib/internal/obfuscated2/conn.go b/mtglib/internal/obfuscated2/conn.go
index 87221c3..511ba62 100644
--- a/mtglib/internal/obfuscated2/conn.go
+++ b/mtglib/internal/obfuscated2/conn.go
@@ -32,5 +32,5 @@ func (c Conn) Write(p []byte) (int, error) {
 	payload := buf.Bytes()
 	c.Encryptor.XORKeyStream(payload, payload)
 
-	return c.Conn.Write(payload)
+	return c.Conn.Write(payload) // nolint: wrapcheck
 }
diff --git a/mtglib/internal/relay/init_test.go b/mtglib/internal/relay/init_test.go
index e19ecf4..d42b825 100644
--- a/mtglib/internal/relay/init_test.go
+++ b/mtglib/internal/relay/init_test.go
@@ -25,7 +25,7 @@ func (r *rwcMock) Read(p []byte) (int, error) {
 		return 0, io.EOF
 	}
 
-	return r.Buffer.Read(p)
+	return r.Buffer.Read(p) // nolint: wrapcheck
 }
 
 func (r *rwcMock) Write(p []byte) (int, error) {
@@ -36,7 +36,7 @@ func (r *rwcMock) Write(p []byte) (int, error) {
 		return 0, io.EOF
 	}
 
-	return r.Buffer.Write(p)
+	return r.Buffer.Write(p) // nolint: wrapcheck
 }
 
 func (r *rwcMock) Close() error {
diff --git a/mtglib/internal/relay/pools.go b/mtglib/internal/relay/pools.go
index 1fae858..091fa8e 100644
--- a/mtglib/internal/relay/pools.go
+++ b/mtglib/internal/relay/pools.go
@@ -18,7 +18,11 @@ var relayPool = sync.Pool{
 func AcquireRelay(ctx context.Context, logger Logger, bufferSize int, idleTimeout time.Duration) *Relay {
 	ctx, cancel := context.WithCancel(ctx)
 
-	r := relayPool.Get().(*Relay)
+	r, ok := relayPool.Get().(*Relay)
+	if !ok {
+		panic("Relay pool has no relay!")
+	}
+
 	r.ctx = ctx
 	r.ctxCancel = cancel
 	r.logger = logger
diff --git a/mtglib/stream_context.go b/mtglib/stream_context.go
index f704f37..7ee8071 100644
--- a/mtglib/stream_context.go
+++ b/mtglib/stream_context.go
@@ -27,7 +27,7 @@ func (s *streamContext) Done() <-chan struct{} {
 }
 
 func (s *streamContext) Err() error {
-	return s.ctx.Err()
+	return s.ctx.Err() // nolint: wrapcheck
 }
 
 func (s *streamContext) Value(key interface{}) interface{} {
diff --git a/network/circuit_breaker.go b/network/circuit_breaker.go
index 4a02bda..4c74a9b 100644
--- a/network/circuit_breaker.go
+++ b/network/circuit_breaker.go
@@ -56,7 +56,7 @@ func (c *circuitBreakerDialer) doClosed(ctx context.Context,
 			conn.Close()
 		}
 
-		return nil, ctx.Err()
+		return nil, ctx.Err() // nolint: wrapcheck
 	case c.stateMutexChan <- true:
 		defer func() {
 			<-c.stateMutexChan
@@ -66,7 +66,7 @@ func (c *circuitBreakerDialer) doClosed(ctx context.Context,
 	if err == nil {
 		c.switchState(circuitBreakerStateClosed)
 
-		return conn, err // nolint: wrapcheck
+		return conn, nil
 	}
 
 	c.failuresCount++
@@ -91,7 +91,7 @@ func (c *circuitBreakerDialer) doHalfOpened(ctx context.Context, network, addres
 			conn.Close()
 		}
 
-		return nil, ctx.Err()
+		return nil, ctx.Err() // nolint: wrapcheck
 	case c.stateMutexChan <- true:
 		defer func() {
 			<-c.stateMutexChan
diff --git a/network/default.go b/network/default.go
index cad8799..7ade79a 100644
--- a/network/default.go
+++ b/network/default.go
@@ -31,7 +31,10 @@ func (d *defaultDialer) DialContext(ctx context.Context, network, address string
 		return nil, fmt.Errorf("cannot dial to %s: %w", address, err)
 	}
 
-	tcpConn := conn.(*net.TCPConn)
+	tcpConn, ok := conn.(*net.TCPConn)
+	if !ok {
+		panic("conn type is not tcp")
+	}
 
 	if err := tcpConn.SetNoDelay(true); err != nil {
 		conn.Close()
diff --git a/network/init_internal_test.go b/network/init_internal_test.go
index 9335818..365a4e5 100644
--- a/network/init_internal_test.go
+++ b/network/init_internal_test.go
@@ -14,11 +14,11 @@ type DialerMock struct {
 func (d *DialerMock) Dial(network, address string) (net.Conn, error) {
 	args := d.Called(network, address)
 
-	return args.Get(0).(net.Conn), args.Error(1)
+	return args.Get(0).(net.Conn), args.Error(1) // nolint: wrapcheck
 }
 
 func (d *DialerMock) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
 	args := d.Called(ctx, network, address)
 
-	return args.Get(0).(net.Conn), args.Error(1)
+	return args.Get(0).(net.Conn), args.Error(1) // nolint: wrapcheck
 }
diff --git a/network/init_test.go b/network/init_test.go
index f42d1c3..f1692e0 100644
--- a/network/init_test.go
+++ b/network/init_test.go
@@ -21,13 +21,13 @@ type DialerMock struct {
 func (d *DialerMock) Dial(network, address string) (net.Conn, error) {
 	args := d.Called(network, address)
 
-	return args.Get(0).(net.Conn), args.Error(1)
+	return args.Get(0).(net.Conn), args.Error(1) // nolint: wrapcheck
 }
 
 func (d *DialerMock) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
 	args := d.Called(ctx, network, address)
 
-	return args.Get(0).(net.Conn), args.Error(1)
+	return args.Get(0).(net.Conn), args.Error(1) // nolint: wrapcheck
 }
 
 type HTTPServerTestSuite struct {
diff --git a/network/network.go b/network/network.go
index 3ff9af6..cac18fb 100644
--- a/network/network.go
+++ b/network/network.go
@@ -20,7 +20,7 @@ type networkHTTPTransport struct {
 func (n networkHTTPTransport) RoundTrip(req *http.Request) (*http.Response, error) {
 	req.Header.Set("User-Agent", n.userAgent)
 
-	return n.next.RoundTrip(req)
+	return n.next.RoundTrip(req) // nolint: wrapcheck
 }
 
 type network struct {
diff --git a/network/proxy_dialer_internal_test.go b/network/proxy_dialer_internal_test.go
index 33aa2b7..8a3e3bb 100644
--- a/network/proxy_dialer_internal_test.go
+++ b/network/proxy_dialer_internal_test.go
@@ -21,7 +21,7 @@ func (suite *ProxyDialerTestSuite) SetupSuite() {
 }
 
 func (suite *ProxyDialerTestSuite) TestSetupDefaults() {
-	d := newProxyDialer(&DialerMock{}, suite.u).(*circuitBreakerDialer)
+	d := newProxyDialer(&DialerMock{}, suite.u).(*circuitBreakerDialer) // nolint: forcetypeassert
 	suite.EqualValues(ProxyDialerOpenThreshold, d.openThreshold)
 	suite.EqualValues(ProxyDialerHalfOpenTimeout, d.halfOpenTimeout)
 	suite.EqualValues(ProxyDialerResetFailuresTimeout, d.resetFailuresTimeout)
@@ -34,7 +34,7 @@ func (suite *ProxyDialerTestSuite) TestSetupValuesAllOk() {
 	query.Set("half_open_timeout", "2s")
 	suite.u.RawQuery = query.Encode()
 
-	d := newProxyDialer(&DialerMock{}, suite.u).(*circuitBreakerDialer)
+	d := newProxyDialer(&DialerMock{}, suite.u).(*circuitBreakerDialer) // nolint: forcetypeassert
 	suite.EqualValues(30, d.openThreshold)
 	suite.EqualValues(2*time.Second, d.halfOpenTimeout)
 	suite.EqualValues(time.Second, d.resetFailuresTimeout)
@@ -50,7 +50,7 @@ func (suite *ProxyDialerTestSuite) TestOpenThreshold() {
 			query.Set("open_threshold", param)
 			suite.u.RawQuery = query.Encode()
 
-			d := newProxyDialer(&DialerMock{}, suite.u).(*circuitBreakerDialer)
+			d := newProxyDialer(&DialerMock{}, suite.u).(*circuitBreakerDialer) // nolint: forcetypeassert
 			assert.EqualValues(t, ProxyDialerOpenThreshold, d.openThreshold)
 		})
 	}
@@ -66,7 +66,7 @@ func (suite *ProxyDialerTestSuite) TestHalfOpenTimeout() {
 			query.Set("half_open_timeout", param)
 			suite.u.RawQuery = query.Encode()
 
-			d := newProxyDialer(&DialerMock{}, suite.u).(*circuitBreakerDialer)
+			d := newProxyDialer(&DialerMock{}, suite.u).(*circuitBreakerDialer) // nolint: forcetypeassert
 			assert.EqualValues(t, ProxyDialerHalfOpenTimeout, d.halfOpenTimeout)
 		})
 	}
@@ -82,7 +82,7 @@ func (suite *ProxyDialerTestSuite) TestResetFailuresTimeout() {
 			query.Set("reset_failures_timeout", param)
 			suite.u.RawQuery = query.Encode()
 
-			d := newProxyDialer(&DialerMock{}, suite.u).(*circuitBreakerDialer)
+			d := newProxyDialer(&DialerMock{}, suite.u).(*circuitBreakerDialer) // nolint: forcetypeassert
 			assert.EqualValues(t, ProxyDialerHalfOpenTimeout, d.halfOpenTimeout)
 		})
 	}
diff --git a/stats/prometheus.go b/stats/prometheus.go
index 634be95..7a22777 100644
--- a/stats/prometheus.go
+++ b/stats/prometheus.go
@@ -158,13 +158,13 @@ func (p *PrometheusFactory) Make() events.Observer {
 
 // Serve starts an HTTP server on a given listener.
 func (p *PrometheusFactory) Serve(listener net.Listener) error {
-	return p.httpServer.Serve(listener)
+	return p.httpServer.Serve(listener) // nolint: wrapcheck
 }
 
 // Close stops a factory. Please pay attention that underlying listener
 // is not closed.
 func (p *PrometheusFactory) Close() error {
-	return p.httpServer.Shutdown(context.Background())
+	return p.httpServer.Shutdown(context.Background()) // nolint: wrapcheck
 }
 
 // NewPrometheus builds an events.ObserverFactory which can serve HTTP
diff --git a/stats/statsd.go b/stats/statsd.go
index f394ec6..fcf8191 100644
--- a/stats/statsd.go
+++ b/stats/statsd.go
@@ -146,7 +146,7 @@ type StatsdFactory struct {
 
 // Close stops sending requests to statsd.
 func (s StatsdFactory) Close() error {
-	return s.client.Close()
+	return s.client.Close() // nolint: wrapcheck
 }
 
 // Make build a new observer.
diff --git a/stats/statsd_test.go b/stats/statsd_test.go
index 4383509..d810c42 100644
--- a/stats/statsd_test.go
+++ b/stats/statsd_test.go
@@ -30,7 +30,7 @@ func (s *statsdFakeServer) Addr() string {
 
 func (s *statsdFakeServer) Close() error {
 	if s.conn != nil {
-		return s.conn.Close()
+		return s.conn.Close() // nolint: wrapcheck
 	}
 
 	return nil