chore: update linter.

.golangci.toml

@@ -54,7 +54,10 @@
     "nestif", # Too many false-positive.
     "noctx", # Too strict
     "exhaustive", # Too strict
-    "nlreturn", # Too strict
+    "nlreturn", # Not relevant
+    "wrapcheck", # Too strict
+    "tparallel", # Not relevant
+    "exhaustivestruct", # Not relevant
   ]
 
 [issues]

build.Dockerfile

@@ -19,7 +19,7 @@ RUN mkdir -p /usr/local/bin \
     && chmod +x /usr/local/bin/go-bindata
 
 # Download golangci-lint binary to bin folder in $GOPATH
-RUN curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | bash -s -- -b $GOPATH/bin v1.31.0
+RUN curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | bash -s -- -b $GOPATH/bin v1.32.2
 
 # Download misspell binary to bin folder in $GOPATH
 RUN  curl -sfL https://raw.githubusercontent.com/client9/misspell/master/install-misspell.sh | bash -s -- -b $GOPATH/bin v0.3.4

go.sum

@@ -1108,6 +1108,7 @@ gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/cheggaaa/pb.v1 v1.0.25/go.mod h1:V/YB90LKu/1FcN3WVnfiiE5oMCibMjukxqG/qStrOgw=
+gopkg.in/errgo.v2 v2.1.0 h1:0vLT13EuvQ0hNvakwLuFZ/jYrLp5F3kcWHXdRggjCE8=
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/fsnotify.v1 v1.4.7 h1:xOHLXZwVvI9hhs+cLKq5+I5onOuwQLhQwiu63xxlHs4=
 gopkg.in/fsnotify.v1 v1.4.7/go.mod h1:Tz8NjZHkW78fSQdbUxIjBTcgA1z1m8ZHf0WmKUhAMys=

pkg/log/log.go

@@ -137,7 +137,7 @@ func RotateFile() error {
 	}
 
 	if err := OpenFile(logFilePath); err != nil {
-		return fmt.Errorf("error opening log file: %s", err)
+		return fmt.Errorf("error opening log file: %w", err)
 	}
 
 	return nil

pkg/metrics/prometheus.go

@@ -2,6 +2,7 @@ package metrics
 
 import (
 	"context"
+	"errors"
 	"net/http"
 	"sort"
 	"strings"
@@ -74,12 +75,15 @@ func RegisterPrometheus(ctx context.Context, config *types.Prometheus) Registry
 	standardRegistry := initStandardRegistry(config)
 
 	if err := promRegistry.Register(stdprometheus.NewProcessCollector(stdprometheus.ProcessCollectorOpts{})); err != nil {
-		if _, ok := err.(stdprometheus.AlreadyRegisteredError); !ok {
+		var arErr stdprometheus.AlreadyRegisteredError
+		if !errors.As(err, &arErr) {
 			log.FromContext(ctx).Warn("ProcessCollector is already registered")
 		}
 	}
+
 	if err := promRegistry.Register(stdprometheus.NewGoCollector()); err != nil {
-		if _, ok := err.(stdprometheus.AlreadyRegisteredError); !ok {
+		var arErr stdprometheus.AlreadyRegisteredError
+		if !errors.As(err, &arErr) {
 			log.FromContext(ctx).Warn("GoCollector is already registered")
 		}
 	}
@@ -212,15 +216,21 @@ func initStandardRegistry(config *types.Prometheus) Registry {
 }
 
 func registerPromState(ctx context.Context) bool {
-	if err := promRegistry.Register(promState); err != nil {
+	err := promRegistry.Register(promState)
-		logger := log.FromContext(ctx)
+	if err == nil {
-		if _, ok := err.(stdprometheus.AlreadyRegisteredError); !ok {
+		return true
-			logger.Errorf("Unable to register Traefik to Prometheus: %v", err)
-			return false
-		}
-		logger.Debug("Prometheus collector already registered.")
 	}
-	return true
+
+	logger := log.FromContext(ctx)
+
+	var arErr stdprometheus.AlreadyRegisteredError
+	if errors.As(err, &arErr) {
+		logger.Debug("Prometheus collector already registered.")
+		return true
+	}
+
+	logger.Errorf("Unable to register Traefik to Prometheus: %v", err)
+	return false
 }
 
 // OnConfigurationUpdate receives the current configuration from Traefik.

pkg/middlewares/auth/forward.go

@@ -2,6 +2,7 @@ package auth
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"net"
@@ -124,7 +125,7 @@ func (fa *forwardAuth) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		redirectURL, err := forwardResponse.Location()
 
 		if err != nil {
-			if err != http.ErrNoLocation {
+			if !errors.Is(err, http.ErrNoLocation) {
 				logMessage := fmt.Sprintf("Error reading response location header %s. Cause: %s", fa.address, err)
 				logger.Debug(logMessage)
 				tracing.SetErrorWithEvent(req, logMessage)

pkg/middlewares/recovery/recovery.go

@@ -54,5 +54,6 @@ func recoverFunc(ctx context.Context, rw http.ResponseWriter, r *http.Request) {
 // https://github.com/golang/go/blob/a0d6420d8be2ae7164797051ec74fa2a2df466a1/src/net/http/server.go#L1761-L1775
 // https://github.com/golang/go/blob/c33153f7b416c03983324b3e8f869ce1116d84bc/src/net/http/httputil/reverseproxy.go#L284
 func shouldLogPanic(panicValue interface{}) bool {
+	//nolint:errorlint // false-positive because panicValue is an interface.
 	return panicValue != nil && panicValue != http.ErrAbortHandler
 }

pkg/provider/docker/docker.go

@@ -2,6 +2,7 @@ package docker
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -307,7 +308,7 @@ func (p *Provider) Provide(configurationChan chan<- dynamic.Message, pool *safe.
 								startStopHandle(event)
 							}
 						case err := <-errc:
-							if err == io.EOF {
+							if errors.Is(err, io.EOF) {
 								logger.Debug("Provider event stream closed")
 							}
 							return err

pkg/server/server.go

@@ -2,6 +2,7 @@ package server
 
 import (
 	"context"
+	"errors"
 	"os"
 	"os/signal"
 	"time"
@@ -85,9 +86,9 @@ func (s *Server) Close() {
 
 	go func(ctx context.Context) {
 		<-ctx.Done()
-		if ctx.Err() == context.Canceled {
+		if errors.Is(ctx.Err(), context.Canceled) {
 			return
-		} else if ctx.Err() == context.DeadlineExceeded {
+		} else if errors.Is(ctx.Err(), context.DeadlineExceeded) {
 			panic("Timeout while stopping traefik, killing instance ✝")
 		}
 	}(ctx)

pkg/server/server_entrypoint_tcp.go

@@ -174,11 +174,15 @@ func (e *TCPEntryPoint) Start(ctx context.Context) {
 		conn, err := e.listener.Accept()
 		if err != nil {
 			logger.Error(err)
-			if netErr, ok := err.(net.Error); ok && netErr.Temporary() {
+
+			var netErr net.Error
+			if errors.As(err, &netErr) && netErr.Temporary() {
 				continue
 			}
+
 			e.httpServer.Forwarder.errChan <- err
 			e.httpsServer.Forwarder.errChan <- err
+
 			return
 		}
 
@@ -232,7 +236,7 @@ func (e *TCPEntryPoint) Shutdown(ctx context.Context) {
 		if err == nil {
 			return
 		}
-		if ctx.Err() == context.DeadlineExceeded {
+		if errors.Is(ctx.Err(), context.DeadlineExceeded) {
 			logger.Debugf("Server failed to shutdown within deadline because: %s", err)
 			if err = server.Close(); err != nil {
 				logger.Error(err)
@@ -263,7 +267,7 @@ func (e *TCPEntryPoint) Shutdown(ctx context.Context) {
 			if err == nil {
 				return
 			}
-			if ctx.Err() == context.DeadlineExceeded {
+			if errors.Is(ctx.Err(), context.DeadlineExceeded) {
 				logger.Debugf("Server failed to shutdown before deadline because: %s", err)
 			}
 			e.tracker.Close()

pkg/server/server_entrypoint_tcp_test.go

@@ -46,7 +46,7 @@ func TestShutdownTCP(t *testing.T) {
 		for {
 			_, err := http.ReadRequest(bufio.NewReader(conn))
 
-			if err == io.EOF || (err != nil && strings.HasSuffix(err.Error(), "use of closed network connection")) {
+			if errors.Is(err, io.EOF) || (err != nil && strings.HasSuffix(err.Error(), "use of closed network connection")) {
 				return
 			}
 			require.NoError(t, err)

pkg/server/service/loadbalancer/mirror/mirror.go

@@ -81,13 +81,13 @@ func (m *Mirroring) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 
 	logger := log.FromContext(req.Context())
 	rr, bytesRead, err := newReusableRequest(req, m.maxBodySize)
-	if err != nil && err != errBodyTooLarge {
+	if err != nil && !errors.Is(err, errBodyTooLarge) {
 		http.Error(rw, http.StatusText(http.StatusInternalServerError)+
 			fmt.Sprintf("error creating reusable request: %v", err), http.StatusInternalServerError)
 		return
 	}
 
-	if err == errBodyTooLarge {
+	if errors.Is(err, errBodyTooLarge) {
 		req.Body = ioutil.NopCloser(io.MultiReader(bytes.NewReader(bytesRead), req.Body))
 		m.handler.ServeHTTP(rw, req)
 		logger.Debugf("no mirroring, request body larger than allowed size")
@@ -196,13 +196,13 @@ func newReusableRequest(req *http.Request, maxBodySize int64) (*reusableRequest,
 	// the request body is larger than what we allow for the mirrors.
 	body := make([]byte, maxBodySize+1)
 	n, err := io.ReadFull(req.Body, body)
-	if err != nil && err != io.ErrUnexpectedEOF {
+	if err != nil && !errors.Is(err, io.ErrUnexpectedEOF) {
 		return nil, nil, err
 	}
 
 	// we got an ErrUnexpectedEOF, which means there was less than maxBodySize data to read,
 	// which permits us sending also to all the mirrors later.
-	if err == io.ErrUnexpectedEOF {
+	if errors.Is(err, io.ErrUnexpectedEOF) {
 		return &reusableRequest{
 			req:  req,
 			body: body[:n],

pkg/server/service/loadbalancer/wrr/wrr.go

@@ -2,6 +2,7 @@ package wrr
 
 import (
 	"container/heap"
+	"errors"
 	"fmt"
 	"net/http"
 	"sync"
@@ -105,7 +106,7 @@ func (b *Balancer) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	if b.stickyCookie != nil {
 		cookie, err := req.Cookie(b.stickyCookie.name)
 
-		if err != nil && err != http.ErrNoCookie {
+		if err != nil && !errors.Is(err, http.ErrNoCookie) {
 			log.WithoutContext().Warnf("Error while reading cookie: %v", err)
 		}
 

pkg/server/service/proxy.go

@@ -2,6 +2,7 @@ package service
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -83,13 +84,14 @@ func buildProxy(passHostHeader *bool, responseForwarding *dynamic.ResponseForwar
 			statusCode := http.StatusInternalServerError
 
 			switch {
-			case err == io.EOF:
+			case errors.Is(err, io.EOF):
 				statusCode = http.StatusBadGateway
-			case err == context.Canceled:
+			case errors.Is(err, context.Canceled):
 				statusCode = StatusClientClosedRequest
 			default:
-				if e, ok := err.(net.Error); ok {
+				var netErr net.Error
-					if e.Timeout() {
+				if errors.As(err, &netErr) {
+					if netErr.Timeout() {
 						statusCode = http.StatusGatewayTimeout
 					} else {
 						statusCode = http.StatusBadGateway

pkg/server/service/proxy_websocket_test.go

@@ -3,6 +3,7 @@ package service
 import (
 	"bufio"
 	"crypto/tls"
+	"errors"
 	"fmt"
 	"net"
 	"net/http"
@@ -49,12 +50,13 @@ func TestWebSocketTCPClose(t *testing.T) {
 		withPath("/ws"),
 	).open()
 	require.NoError(t, err)
+
 	conn.Close()
 
 	serverErr := <-errChan
 
-	wsErr, ok := serverErr.(*gorillawebsocket.CloseError)
+	var wsErr *gorillawebsocket.CloseError
-	assert.Equal(t, true, ok)
+	require.True(t, errors.As(serverErr, &wsErr))
 	assert.Equal(t, 1006, wsErr.Code)
 }
 
@@ -119,7 +121,7 @@ func TestWebSocketPingPong(t *testing.T) {
 
 	_, _, err = conn.ReadMessage()
 
-	if err != goodErr {
+	if !errors.Is(err, goodErr) {
 		require.NoError(t, err)
 	}
 }

pkg/tcp/router.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"crypto/tls"
+	"errors"
 	"io"
 	"net"
 	"net/http"
@@ -197,10 +198,11 @@ func (c *Conn) Read(p []byte) (n int, err error) {
 func clientHelloServerName(br *bufio.Reader) (string, bool, string, error) {
 	hdr, err := br.Peek(1)
 	if err != nil {
-		opErr, ok := err.(*net.OpError)
+		var opErr *net.OpError
-		if err != io.EOF && (!ok || !opErr.Timeout()) {
+		if !errors.Is(err, io.EOF) && (!errors.As(err, &opErr) || opErr.Timeout()) {
 			log.WithoutContext().Debugf("Error while Peeking first byte: %s", err)
 		}
+
 		return "", false, "", err
 	}
 

pkg/udp/conn_test.go

@@ -1,6 +1,7 @@
 package udp
 
 import (
+	"errors"
 	"io"
 	"net"
 	"testing"
@@ -24,7 +25,7 @@ func TestConsecutiveWrites(t *testing.T) {
 	go func() {
 		for {
 			conn, err := ln.Accept()
-			if err == errClosedListener {
+			if errors.Is(err, errClosedListener) {
 				return
 			}
 			require.NoError(t, err)
@@ -86,7 +87,7 @@ func TestListenNotBlocking(t *testing.T) {
 	go func() {
 		for {
 			conn, err := ln.Accept()
-			if err == errClosedListener {
+			if errors.Is(err, errClosedListener) {
 				return
 			}
 			require.NoError(t, err)
@@ -183,7 +184,7 @@ func testTimeout(t *testing.T, withRead bool) {
 	go func() {
 		for {
 			conn, err := ln.Accept()
-			if err == errClosedListener {
+			if errors.Is(err, errClosedListener) {
 				return
 			}
 			require.NoError(t, err)