fix Span{Logger *Logger}

tlog.go

@@ -36,7 +36,7 @@ type (
 	}
 
 	Span struct {
-		*Logger
+		Logger    *Logger
 		ID        ID
 		StartedAt time.Time
 	}
@@ -441,6 +441,9 @@ func (l *Logger) Write(p []byte) (int, error) {
 	return l.Writer.Write(p)
 }
 
+func (l *Logger) OK() bool { return l != nil }
+func (s Span) OK() bool    { return s.Logger != nil }
+
 func LoggerSetTimeNow(l *Logger, now func() time.Time, nano func() int64) {
 	l.now = now
 	l.nano = nano