decrypt ETags in parallel around 500 at a time (#10261)

Listing speed-up gained from 10secs for
just 400 entries to 2secs for 400 entries

cmd/crypto/header.go

@@ -18,10 +18,10 @@ import (
 	"bytes"
 	"crypto/md5"
 	"encoding/base64"
-	"encoding/json"
 	"net/http"
 	"strings"
 
+	jsoniter "github.com/json-iterator/go"
 	xhttp "github.com/minio/minio/cmd/http"
 )
 
@@ -148,6 +148,7 @@ func (s3KMS) ParseHTTP(h http.Header) (string, interface{}, error) {
 	contextStr, ok := h[SSEKmsContext]
 	if ok {
 		var context map[string]interface{}
+		var json = jsoniter.ConfigCompatibleWithStandardLibrary
 		if err := json.Unmarshal([]byte(contextStr[0]), &context); err != nil {
 			return "", nil, err
 		}

cmd/crypto/kes.go

@@ -18,7 +18,6 @@ import (
 	"bytes"
 	"crypto/tls"
 	"crypto/x509"
-	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -30,10 +29,13 @@ import (
 	"strings"
 	"time"
 
+	jsoniter "github.com/json-iterator/go"
 	xhttp "github.com/minio/minio/cmd/http"
 	xnet "github.com/minio/minio/pkg/net"
 )
 
+var json = jsoniter.ConfigCompatibleWithStandardLibrary
+
 // ErrKESKeyExists is the error returned a KES server
 // when a master key does exist.
 var ErrKESKeyExists = NewKESError(http.StatusBadRequest, "key does already exist")