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/fds.go

@@ -20,14 +20,14 @@
 package sys
 
 import (
-	"io/ioutil"
+	"os"
 	"path/filepath"
 	"strconv"
 )
 
 // GetOpenFds returns the number of open fds for the process provided by pid
 func GetOpenFds(pid int) (int, error) {
-	dirs, err := ioutil.ReadDir(filepath.Join("/proc", strconv.Itoa(pid), "fd"))
+	dirs, err := os.ReadDir(filepath.Join("/proc", strconv.Itoa(pid), "fd"))
 	if err != nil {
 		return -1, err
 	}

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
 	}