refactor: use os.ReadDir for lightweight directory reading

This commit also replaces the existing io/ioutil functions with their
new definitions in io and os packages, since the io/ioutil package has
been deprecated as of Go 1.16, see https://golang.org/doc/go1.16#ioutil.

Reference: https://pkg.go.dev/io/ioutil#ReadDir
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

internal/metrics/collectors/processes.go

@@ -3,7 +3,7 @@ package collectors
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
+	"os"
 	"strconv"
 
 	"github.com/golang/glog"
@@ -45,7 +45,7 @@ func getWorkerProcesses() (int, int, error) {
 	var workerProcesses int
 	var prevWorkerProcesses int
 
-	procFolders, err := ioutil.ReadDir("/proc")
+	procFolders, err := os.ReadDir("/proc")
 	if err != nil {
 		return 0, 0, fmt.Errorf("unable to read directory /proc : %w", err)
 	}
@@ -57,7 +57,7 @@ func getWorkerProcesses() (int, int, error) {
 		}
 
 		cmdlineFile := fmt.Sprintf("/proc/%v/cmdline", folder.Name())
-		content, err := ioutil.ReadFile(cmdlineFile)
+		content, err := os.ReadFile(cmdlineFile)
 		if err != nil {
 			return 0, 0, fmt.Errorf("unable to read file %v: %w", cmdlineFile, err)
 		}

internal/metrics/listener.go

@@ -2,7 +2,6 @@ package metrics
 
 import (
 	"fmt"
-	"io/ioutil"
 	"net/http"
 	"os"
 	"strconv"
@@ -75,7 +74,7 @@ func runServer(port string, registry prometheus.Gatherer, prometheusSecret *api_
 }
 
 func writeTempFile(data []byte, name string) (*os.File, error) {
-	f, err := ioutil.TempFile("", name)
+	f, err := os.CreateTemp("", name)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create temp file: %w", err)
 	}

internal/nginx/manager.go

@@ -2,7 +2,6 @@ package nginx
 
 import (
 	"fmt"
-	"io/ioutil"
 	"net/http"
 	"os"
 	"os/exec"
@@ -265,7 +264,7 @@ func (lm *LocalManager) DeleteAppProtectResourceFile(name string) {
 
 // ClearAppProtectFolder clears contents of a config folder
 func (lm *LocalManager) ClearAppProtectFolder(name string) {
-	files, err := ioutil.ReadDir(name)
+	files, err := os.ReadDir(name)
 	if err != nil {
 		glog.Fatalf("Failed to read the App Protect folder %s: %v", name, err)
 	}

internal/nginx/utils.go

@@ -3,7 +3,6 @@ package nginx
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"path"
@@ -51,7 +50,7 @@ func createFileAndWrite(name string, b []byte) error {
 }
 
 func createFileAndWriteAtomically(filename string, tempPath string, mode os.FileMode, content []byte) {
-	file, err := ioutil.TempFile(tempPath, path.Base(filename))
+	file, err := os.CreateTemp(tempPath, path.Base(filename))
 	if err != nil {
 		glog.Fatalf("Couldn't create a temp file for the file %v: %v", filename, err)
 	}

internal/nginx/verify.go

@@ -5,7 +5,7 @@ import (
 	"context"
 	"fmt"
 	"html/template"
-	"io/ioutil"
+	"io"
 	"net"
 	"net/http"
 	"strconv"
@@ -47,7 +47,7 @@ func (c *verifyClient) GetConfigVersion() (int, error) {
 		return 0, fmt.Errorf("non-200 response: %v", resp.StatusCode)
 	}
 
-	body, err := ioutil.ReadAll(resp.Body)
+	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return 0, fmt.Errorf("failed to read the response body: %w", err)
 	}

internal/nginx/verify_test.go

@@ -2,7 +2,7 @@ package nginx
 
 import (
 	"bytes"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"strings"
 	"testing"
@@ -14,7 +14,7 @@ type Transport struct{}
 func (c Transport) RoundTrip(_ *http.Request) (*http.Response, error) {
 	return &http.Response{
 		StatusCode: 200,
-		Body:       ioutil.NopCloser(bytes.NewBufferString("42")),
+		Body:       io.NopCloser(bytes.NewBufferString("42")),
 		Header:     make(http.Header),
 	}, nil
 }