refactor: move from io/ioutil to io and os package

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

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

sys/oom_linux.go

@@ -18,7 +18,6 @@ package sys
 
 import (
 	"fmt"
-	"io/ioutil"
 	"os"
 	"strconv"
 	"strings"
@@ -69,7 +68,7 @@ func SetOOMScore(pid, score int) error {
 // no oom score is set, or a sore is set to 0.
 func GetOOMScoreAdj(pid int) (int, error) {
 	path := fmt.Sprintf("/proc/%d/oom_score_adj", pid)
-	data, err := ioutil.ReadFile(path)
+	data, err := os.ReadFile(path)
 	if err != nil {
 		return 0, err
 	}