Add defered syslog hook

Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au>

vendor/github.com/Sirupsen/logrus/json_formatter.go

@@ -5,9 +5,40 @@ import (
 	"fmt"
 )
 
+type fieldKey string
+type FieldMap map[fieldKey]string
+
+const (
+	FieldKeyMsg   = "msg"
+	FieldKeyLevel = "level"
+	FieldKeyTime  = "time"
+)
+
+func (f FieldMap) resolve(key fieldKey) string {
+	if k, ok := f[key]; ok {
+		return k
+	}
+
+	return string(key)
+}
+
 type JSONFormatter struct {
 	// TimestampFormat sets the format used for marshaling timestamps.
 	TimestampFormat string
+
+	// DisableTimestamp allows disabling automatic timestamps in output
+	DisableTimestamp bool
+
+	// FieldMap allows users to customize the names of keys for various fields.
+	// As an example:
+	// formatter := &JSONFormatter{
+	//   	FieldMap: FieldMap{
+	// 		 FieldKeyTime: "@timestamp",
+	// 		 FieldKeyLevel: "@level",
+	// 		 FieldKeyLevel: "@message",
+	//    },
+	// }
+	FieldMap FieldMap
 }
 
 func (f *JSONFormatter) Format(entry *Entry) ([]byte, error) {
@@ -29,9 +60,11 @@ func (f *JSONFormatter) Format(entry *Entry) ([]byte, error) {
 		timestampFormat = DefaultTimestampFormat
 	}
 
-	data["time"] = entry.Time.Format(timestampFormat)
-	data["msg"] = entry.Message
-	data["level"] = entry.Level.String()
+	if !f.DisableTimestamp {
+		data[f.FieldMap.resolve(FieldKeyTime)] = entry.Time.Format(timestampFormat)
+	}
+	data[f.FieldMap.resolve(FieldKeyMsg)] = entry.Message
+	data[f.FieldMap.resolve(FieldKeyLevel)] = entry.Level.String()
 
 	serialized, err := json.Marshal(data)
 	if err != nil {