Refactor: move from io/ioutil to io and os package (#2234)

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 <zerjun@beatchain.co>

pkg/controller/core.oam.dev/v1alpha2/application/assemble/assemble_suite_test.go

@@ -17,7 +17,7 @@ limitations under the License.
 package assemble
 
 import (
-	"io/ioutil"
+	"os"
 	"testing"
 
 	. "github.com/onsi/ginkgo"
@@ -43,7 +43,7 @@ var _ = Describe("Test Assemble Options", func() {
 		)
 
 		appRev := &v1beta1.ApplicationRevision{}
-		b, err := ioutil.ReadFile("./testdata/apprevision.yaml")
+		b, err := os.ReadFile("./testdata/apprevision.yaml")
 		/* appRevision test data is generated based on below application
 		apiVersion: core.oam.dev/v1beta1
 		kind: Application
@@ -156,7 +156,7 @@ var _ = Describe("Test Assemble Options", func() {
 			compName = "frontend"
 		)
 		appRev := &v1beta1.ApplicationRevision{}
-		b, err := ioutil.ReadFile("./testdata/filter_annotations.yaml")
+		b, err := os.ReadFile("./testdata/filter_annotations.yaml")
 		getKeys := func(m map[string]string) []string {
 			var keys []string
 			for k := range m {

pkg/controller/core.oam.dev/v1alpha2/application/assemble/options_test.go

@@ -19,7 +19,7 @@ package assemble
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
+	"os"
 	"reflect"
 
 	"github.com/google/go-cmp/cmp"
@@ -49,7 +49,7 @@ var _ = Describe("Test WorkloadOption", func() {
 
 	BeforeEach(func() {
 		appRev = &v1beta1.ApplicationRevision{}
-		b, err := ioutil.ReadFile("./testdata/apprevision.yaml")
+		b, err := os.ReadFile("./testdata/apprevision.yaml")
 		Expect(err).Should(BeNil())
 		err = yaml.Unmarshal(b, appRev)
 		Expect(err).Should(BeNil())

pkg/controller/core.oam.dev/v1alpha2/applicationconfiguration/component_custom_revision.go

@@ -21,7 +21,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 
 	"sigs.k8s.io/controller-runtime/pkg/reconcile"
@@ -61,7 +61,7 @@ func (c *ComponentHandler) customComponentRevisionHook(relatedApps []reconcile.R
 	}
 	//nolint:errcheck
 	defer resp.Body.Close()
-	respData, err := ioutil.ReadAll(resp.Body)
+	respData, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return err
 	}

pkg/controller/core.oam.dev/v1alpha2/applicationconfiguration/component_custom_revision_test.go

@@ -19,7 +19,7 @@ package applicationconfiguration
 import (
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -36,7 +36,7 @@ import (
 
 var RevisionHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 	var req RevisionHookRequest
-	data, err := ioutil.ReadAll(r.Body)
+	data, err := io.ReadAll(r.Body)
 	if err != nil {
 		w.WriteHeader(400)
 		return