refactor(plugins): replace deprecated io/ioutil functions

The io/ioutil package has been deprecated as of Go 1.16 [1]. This commit
replaces the existing io/ioutil functions with their new definitions in
io and os packages.

[1]: https://golang.org/doc/go1.16#ioutil
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

plugins/app-json/functions.go

@@ -6,7 +6,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -85,7 +84,7 @@ func getAppJSON(appName string) (AppJSON, error) {
 		return AppJSON{}, nil
 	}
 
-	b, err := ioutil.ReadFile(getProcessSpecificAppJSONPath(appName))
+	b, err := os.ReadFile(getProcessSpecificAppJSONPath(appName))
 	if err != nil {
 		return AppJSON{}, fmt.Errorf("Cannot read app.json file: %v", err)
 	}