chore: remove refs to deprecated io/ioutil

pkg/custompluginmonitor/custom_plugin_monitor.go

@@ -18,7 +18,7 @@ package custompluginmonitor
 
 import (
 	"encoding/json"
-	"io/ioutil"
+	"os"
 	"time"
 
 	"github.com/golang/glog"
@@ -57,7 +57,7 @@ func NewCustomPluginMonitorOrDie(configPath string) types.Monitor {
 		configPath: configPath,
 		tomb:       tomb.NewTomb(),
 	}
-	f, err := ioutil.ReadFile(configPath)
+	f, err := os.ReadFile(configPath)
 	if err != nil {
 		glog.Fatalf("Failed to read configuration file %q: %v", configPath, err)
 	}

pkg/custompluginmonitor/plugin/plugin.go

@@ -20,7 +20,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os/exec"
 	"strings"
 	"sync"
@@ -132,12 +131,12 @@ func (p *Plugin) runRules() {
 // readFromReader reads the maxBytes from the reader and drains the rest.
 func readFromReader(reader io.ReadCloser, maxBytes int64) ([]byte, error) {
 	limitReader := io.LimitReader(reader, maxBytes)
-	data, err := ioutil.ReadAll(limitReader)
+	data, err := io.ReadAll(limitReader)
 	if err != nil {
 		return []byte{}, err
 	}
 	// Drain the reader
-	if _, err := io.Copy(ioutil.Discard, reader); err != nil {
+	if _, err := io.Copy(io.Discard, reader); err != nil {
 		return []byte{}, err
 	}
 	return data, nil