fix golint issues in core/jsonx (#491)

core/jsonx/json.go

@@ -8,10 +8,12 @@ import (
 	"strings"
 )
 
+// Marshal marshals v into json bytes.
 func Marshal(v interface{}) ([]byte, error) {
 	return json.Marshal(v)
 }
 
+// Unmarshal unmarshals data bytes into v.
 func Unmarshal(data []byte, v interface{}) error {
 	decoder := json.NewDecoder(bytes.NewReader(data))
 	if err := unmarshalUseNumber(decoder, v); err != nil {
@@ -21,6 +23,7 @@ func Unmarshal(data []byte, v interface{}) error {
 	return nil
 }
 
+// UnmarshalFromString unmarshals v from str.
 func UnmarshalFromString(str string, v interface{}) error {
 	decoder := json.NewDecoder(strings.NewReader(str))
 	if err := unmarshalUseNumber(decoder, v); err != nil {
@@ -30,6 +33,7 @@ func UnmarshalFromString(str string, v interface{}) error {
 	return nil
 }
 
+// UnmarshalFromReader unmarshals v from reader.
 func UnmarshalFromReader(reader io.Reader, v interface{}) error {
 	var buf strings.Builder
 	teeReader := io.TeeReader(reader, &buf)