Default time format is RFC3339Nano

Signed-off-by: Vishal Rana <vr@labstack.com>

log/log.go

@@ -46,7 +46,7 @@ const (
 
 var (
 	global        = New("-")
-	defaultHeader = `{"time":"${time_rfc3339}","level":"${level}","prefix":"${prefix}",` +
+	defaultHeader = `{"time":"${time_rfc3339_nano}","level":"${level}","prefix":"${prefix}",` +
 		`"file":"${short_file}","line":"${line}"}`
 )
 
@@ -363,6 +363,8 @@ func (l *Logger) log(v Lvl, format string, args ...interface{}) {
 			switch tag {
 			case "time_rfc3339":
 				return w.Write([]byte(time.Now().Format(time.RFC3339)))
+			case "time_rfc3339_nano":
+				return w.Write([]byte(time.Now().Format(time.RFC3339Nano)))
 			case "level":
 				return w.Write([]byte(l.levels[v]))
 			case "prefix":