chore: Fix warnings

Fixing warnings in cloudflared log collector.

This attempts to fix errors like the ones shown below:

```
diagnostic/diagnostic.go:132:23: Error return value of `logHandle.Close` is not checked (errcheck)
	defer logHandle.Close()

diagnostic/diagnostic.go:134:26: G303: File creation in shared tmp directory without using ioutil.Tempfile (gosec)
	outputLogHandle, err := os.Create(filepath.Join(os.TempDir(), logFilename))
```

cmd/cloudflared/tunnel/subcommands.go

@@ -421,7 +421,7 @@ func listCommand(c *cli.Context) error {
 
 func formatAndPrintTunnelList(tunnels []*cfapi.Tunnel, showRecentlyDisconnected bool) {
 	writer := tabWriter()
-	defer writer.Flush()
+	defer func() { _ = writer.Flush() }()
 
 	_, _ = fmt.Fprintln(writer, "You can obtain more detailed information for each tunnel with `cloudflared tunnel info <name/uuid>`")
 
@@ -444,13 +444,14 @@ func formatAndPrintTunnelList(tunnels []*cfapi.Tunnel, showRecentlyDisconnected
 func fmtConnections(connections []cfapi.Connection, showRecentlyDisconnected bool) string {
 	// Count connections per colo
 	numConnsPerColo := make(map[string]uint, len(connections))
-	for _, connection := range connections {
-		if !connection.IsPendingReconnect || showRecentlyDisconnected {
-			numConnsPerColo[connection.ColoName]++
+	for _, cfConnections := range connections {
+		if !cfConnections.IsPendingReconnect || showRecentlyDisconnected {
+			numConnsPerColo[cfConnections.ColoName]++
 		}
 	}
 
 	// Get sorted list of colos
+	// nolint: prealloc
 	sortedColos := []string{}
 	for coloName := range numConnsPerColo {
 		sortedColos = append(sortedColos, coloName)
@@ -488,11 +489,12 @@ func readyCommand(c *cli.Context) error {
 	if err != nil {
 		return err
 	}
+	// nolint: gosec
 	res, err := http.DefaultClient.Do(req)
 	if err != nil {
 		return err
 	}
-	defer res.Body.Close()
+	defer func() { _ = res.Body.Close() }()
 	if res.StatusCode != 200 {
 		body, err := io.ReadAll(res.Body)
 		if err != nil {
@@ -613,7 +615,7 @@ func getTunnel(sc *subcommandContext, tunnelID uuid.UUID) (*cfapi.Tunnel, error)
 
 func formatAndPrintConnectionsList(tunnelInfo Info, showRecentlyDisconnected bool) {
 	writer := tabWriter()
-	defer writer.Flush()
+	defer func() { _ = writer.Flush() }()
 
 	// Print the general tunnel info table
 	_, _ = fmt.Fprintf(writer, "NAME:     %s\nID:       %s\nCREATED:  %s\n\n", tunnelInfo.Name, tunnelInfo.ID, tunnelInfo.CreatedAt)
@@ -654,14 +656,14 @@ func formatAndPrintConnectionsList(tunnelInfo Info, showRecentlyDisconnected boo
 
 func tabWriter() *tabwriter.Writer {
 	const (
-		minWidth = 0
-		tabWidth = 8
-		padding  = 1
-		padChar  = ' '
-		flags    = 0
+		minWidth    = 0
+		tabWidth    = 8
+		padding     = 1
+		padChar     = ' '
+		formatFlags = 0
 	)
 
-	writer := tabwriter.NewWriter(os.Stdout, minWidth, tabWidth, padding, padChar, flags)
+	writer := tabwriter.NewWriter(os.Stdout, minWidth, tabWidth, padding, padChar, formatFlags)
 	return writer
 }
 
@@ -712,7 +714,8 @@ func renderOutput(format string, v interface{}) error {
 }
 
 func buildRunCommand() *cli.Command {
-	flags := []cli.Flag{
+	//nolint: prealloc
+	cliFlags := []cli.Flag{
 		credentialsFileFlag,
 		credentialsContentsFlag,
 		postQuantumFlag,
@@ -725,7 +728,7 @@ func buildRunCommand() *cli.Command {
 		maxActiveFlowsFlag,
 		dnsResolverAddrsFlag,
 	}
-	flags = append(flags, configureProxyFlags(false)...)
+	cliFlags = append(cliFlags, configureProxyFlags(false)...)
 	return &cli.Command{
 		Name:      "run",
 		Action:    cliutil.ConfiguredAction(runCommand),
@@ -740,7 +743,7 @@ func buildRunCommand() *cli.Command {
   If you experience other problems running the tunnel, "cloudflared tunnel cleanup" may help by removing
   any old connection records.
 `,
-		Flags:              flags,
+		Flags:              cliFlags,
 		CustomHelpTemplate: commandHelpTemplate(),
 	}
 }
@@ -765,6 +768,7 @@ func runCommand(c *cli.Context) error {
 	// Check if tokenStr is blank before checking for tokenFile
 	if tokenStr == "" {
 		if tokenFile := c.String(TunnelTokenFileFlag); tokenFile != "" {
+			// nolint: gosec
 			data, err := os.ReadFile(tokenFile)
 			if err != nil {
 				return cliutil.UsageError("Failed to read token file: %s", err.Error())

diagnostic/diagnostic.go

@@ -126,13 +126,14 @@ func collectLogs(
 	if err != nil {
 		return "", fmt.Errorf("error opening log file while collecting logs: %w", err)
 	}
-	defer logHandle.Close()
+	defer func() { _ = logHandle.Close() }()
 
+	// nolint: gosec
 	outputLogHandle, err := os.Create(filepath.Join(os.TempDir(), logFilename))
 	if err != nil {
 		return "", ErrCreatingTemporaryFile
 	}
-	defer outputLogHandle.Close()
+	defer func() { _ = outputLogHandle.Close() }()
 
 	_, err = io.Copy(outputLogHandle, logHandle)
 	if err != nil {
@@ -229,12 +230,13 @@ func networkInformationCollectors() (rawNetworkCollector, jsonNetworkCollector c
 }
 
 func rawNetworkInformationWriter(resultMap map[string]networkCollectionResult) (string, error) {
+	// nolint: gosec
 	networkDumpHandle, err := os.Create(filepath.Join(os.TempDir(), rawNetworkBaseName))
 	if err != nil {
 		return "", ErrCreatingTemporaryFile
 	}
 
-	defer networkDumpHandle.Close()
+	defer func() { _ = networkDumpHandle.Close() }()
 
 	var exitErr error
 
@@ -260,12 +262,13 @@ func rawNetworkInformationWriter(resultMap map[string]networkCollectionResult) (
 }
 
 func jsonNetworkInformationWriter(resultMap map[string]networkCollectionResult) (string, error) {
+	// nolint: gosec
 	networkDumpHandle, err := os.Create(filepath.Join(os.TempDir(), networkBaseName))
 	if err != nil {
 		return "", ErrCreatingTemporaryFile
 	}
 
-	defer networkDumpHandle.Close()
+	defer func() { _ = networkDumpHandle.Close() }()
 
 	encoder := newFormattedEncoder(networkDumpHandle)
 
@@ -290,11 +293,12 @@ func jsonNetworkInformationWriter(resultMap map[string]networkCollectionResult)
 
 func collectFromEndpointAdapter(collect collectToWriterFunc, fileName string) collectFunc {
 	return func(ctx context.Context) (string, error) {
+		// nolint: gosec
 		dumpHandle, err := os.Create(filepath.Join(os.TempDir(), fileName))
 		if err != nil {
 			return "", ErrCreatingTemporaryFile
 		}
-		defer dumpHandle.Close()
+		defer func() { _ = dumpHandle.Close() }()
 
 		err = collect(ctx, dumpHandle)
 		if err != nil {
@@ -349,12 +353,12 @@ func resolveInstanceBaseURL(
 		if !strings.HasPrefix(metricsServerAddress, "http://") {
 			metricsServerAddress = "http://" + metricsServerAddress
 		}
-		url, err := url.Parse(metricsServerAddress)
+		baseUrl, err := url.Parse(metricsServerAddress)
 		if err != nil {
 			return nil, nil, nil, fmt.Errorf("provided address is not valid: %w", err)
 		}
 
-		return url, nil, nil, nil
+		return baseUrl, nil, nil, nil
 	}
 
 	tunnelState, foundTunnelStates, err := FindMetricsServer(log, client, addresses)
@@ -436,11 +440,12 @@ func createJobs(
 }
 
 func createTaskReport(taskReport map[string]taskResult) (string, error) {
+	// nolint: gosec
 	dumpHandle, err := os.Create(filepath.Join(os.TempDir(), taskResultBaseName))
 	if err != nil {
 		return "", ErrCreatingTemporaryFile
 	}
-	defer dumpHandle.Close()
+	defer func() { _ = dumpHandle.Close() }()
 
 	encoder := newFormattedEncoder(dumpHandle)
 
@@ -545,7 +550,7 @@ func RunDiagnostic(
 
 		defer func() {
 			if !errors.Is(v.Err, ErrCreatingTemporaryFile) {
-				os.Remove(v.path)
+				_ = os.Remove(v.path)
 			}
 		}()
 	}

diagnostic/log_collector_docker.go

@@ -20,18 +20,18 @@ func NewDockerLogCollector(containerID string) *DockerLogCollector {
 }
 
 func (collector *DockerLogCollector) Collect(ctx context.Context) (*LogInformation, error) {
-	tmp := os.TempDir()
-
-	outputHandle, err := os.Create(filepath.Join(tmp, logFilename))
+	// nolint: gosec
+	outputHandle, err := os.Create(filepath.Join(os.TempDir(), logFilename))
 	if err != nil {
 		return nil, fmt.Errorf("error opening output file: %w", err)
 	}
 
-	defer outputHandle.Close()
+	defer func() { _ = outputHandle.Close() }()
 
 	// Calculate 2 weeks ago
 	since := time.Now().Add(twoWeeksOffset).Format(time.RFC3339)
 
+	// nolint: gosec
 	command := exec.CommandContext(
 		ctx,
 		"docker",

diagnostic/log_collector_host.go

@@ -13,7 +13,6 @@ const (
 	linuxManagedLogsPath          = "/var/log/cloudflared.err"
 	darwinManagedLogsPath         = "/Library/Logs/com.cloudflare.cloudflared.err.log"
 	linuxServiceConfigurationPath = "/etc/systemd/system/cloudflared.service"
-	linuxSystemdPath              = "/run/systemd/system"
 )
 
 type HostLogCollector struct {
@@ -27,14 +26,13 @@ func NewHostLogCollector(client HTTPClient) *HostLogCollector {
 }
 
 func extractLogsFromJournalCtl(ctx context.Context) (*LogInformation, error) {
-	tmp := os.TempDir()
-
-	outputHandle, err := os.Create(filepath.Join(tmp, logFilename))
+	// nolint: gosec
+	outputHandle, err := os.Create(filepath.Join(os.TempDir(), logFilename))
 	if err != nil {
 		return nil, fmt.Errorf("error opening output file: %w", err)
 	}
 
-	defer outputHandle.Close()
+	defer func() { _ = outputHandle.Close() }()
 
 	command := exec.CommandContext(
 		ctx,

diagnostic/log_collector_kubernetes.go

@@ -22,18 +22,19 @@ func NewKubernetesLogCollector(containerID, pod string) *KubernetesLogCollector
 }
 
 func (collector *KubernetesLogCollector) Collect(ctx context.Context) (*LogInformation, error) {
-	tmp := os.TempDir()
-	outputHandle, err := os.Create(filepath.Join(tmp, logFilename))
+	// nolint: gosec
+	outputHandle, err := os.Create(filepath.Join(os.TempDir(), logFilename))
 	if err != nil {
 		return nil, fmt.Errorf("error opening output file: %w", err)
 	}
 
-	defer outputHandle.Close()
+	defer func() { _ = outputHandle.Close() }()
 
 	var command *exec.Cmd
 	// Calculate 2 weeks ago
 	since := time.Now().Add(twoWeeksOffset).Format(time.RFC3339)
 	if collector.containerID != "" {
+		// nolint: gosec
 		command = exec.CommandContext(
 			ctx,
 			"kubectl",
@@ -47,6 +48,7 @@ func (collector *KubernetesLogCollector) Collect(ctx context.Context) (*LogInfor
 			collector.containerID,
 		)
 	} else {
+		// nolint: gosec
 		command = exec.CommandContext(
 			ctx,
 			"kubectl",

diagnostic/log_collector_utils.go

@@ -67,6 +67,8 @@ func PipeCommandOutputToFile(command *exec.Cmd, outputHandle *os.File) (*LogInfo
 }
 
 func CopyFilesFromDirectory(path string) (string, error) {
+	const defaultLogFilename = "cloudflared.log"
+
 	// rolling logs have as suffix the current date thus
 	// when iterating the path files they are already in
 	// chronological order
@@ -75,30 +77,32 @@ func CopyFilesFromDirectory(path string) (string, error) {
 		return "", fmt.Errorf("error reading directory %s: %w", path, err)
 	}
 
+	// nolint: gosec
 	outputHandle, err := os.Create(filepath.Join(os.TempDir(), logFilename))
 	if err != nil {
-		return "", fmt.Errorf("creating file %s: %w", outputHandle.Name(), err)
+		return "", fmt.Errorf("creating temporary log file %s: %w", logFilename, err)
 	}
-	defer outputHandle.Close()
+	defer func() { _ = outputHandle.Close() }()
 
 	for _, file := range files {
+		// nolint: gosec
 		logHandle, err := os.Open(filepath.Join(path, file.Name()))
 		if err != nil {
-			return "", fmt.Errorf("error opening file %s:%w", file.Name(), err)
+			return "", fmt.Errorf("error opening file %s: %w", file.Name(), err)
 		}
-		defer logHandle.Close()
-
 		_, err = io.Copy(outputHandle, logHandle)
+		_ = logHandle.Close()
 		if err != nil {
-			return "", fmt.Errorf("error copying file %s:%w", logHandle.Name(), err)
+			return "", fmt.Errorf("error copying file %s: %w", file.Name(), err)
 		}
 	}
 
-	logHandle, err := os.Open(filepath.Join(path, "cloudflared.log"))
+	// nolint: gosec
+	logHandle, err := os.Open(filepath.Join(path, defaultLogFilename))
 	if err != nil {
-		return "", fmt.Errorf("error opening file %s:%w", logHandle.Name(), err)
+		return "", fmt.Errorf("error opening file %s:%w", defaultLogFilename, err)
 	}
-	defer logHandle.Close()
+	defer func() { _ = logHandle.Close() }()
 
 	_, err = io.Copy(outputHandle, logHandle)
 	if err != nil {