refactor: move from io/ioutil to io and os package (#2236)

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>

pkg/fission-cli/cmd/spec/apply.go

@@ -19,7 +19,6 @@ package spec
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -487,7 +486,7 @@ func localArchiveFromSpec(specDir string, aus *spectypes.ArchiveUploadSpec) (*fv
 
 	if len(files) > 1 || !isSingleFile {
 		// zip up the file list
-		archiveFile, err := ioutil.TempFile("", fmt.Sprintf("fission-archive-%v", aus.Name))
+		archiveFile, err := os.CreateTemp("", fmt.Sprintf("fission-archive-%v", aus.Name))
 		if err != nil {
 			return nil, err
 		}

pkg/fission-cli/cmd/spec/init.go

@@ -18,7 +18,6 @@ package spec
 
 import (
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 
@@ -110,7 +109,7 @@ func (opts *InitSubCommand) run(input cli.Input) error {
 	}
 
 	// Add a bit of documentation to the spec dir here
-	err := ioutil.WriteFile(readme, []byte(SPEC_README), 0644)
+	err := os.WriteFile(readme, []byte(SPEC_README), 0644)
 	if err != nil {
 		return err
 	}
@@ -138,7 +137,7 @@ func writeDeploymentConfig(file string, dc *spectypes.DeploymentConfig) error {
 		"# See the README in this directory for background and usage information.\n" +
 		"# Do not edit the UID below: that will break 'fission spec apply'\n")
 
-	err = ioutil.WriteFile(file, append(msg, y...), 0644)
+	err = os.WriteFile(file, append(msg, y...), 0644)
 	if err != nil {
 		return err
 	}

pkg/fission-cli/cmd/spec/validate.go

@@ -19,7 +19,6 @@ package spec
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -234,7 +233,7 @@ func ReadSpecs(specDir string) (*FissionResources, error) {
 			return nil
 		}
 		// read
-		b, err := ioutil.ReadFile(path)
+		b, err := os.ReadFile(path)
 		if err != nil {
 			result = multierror.Append(result, err)
 			return nil