fix: add comment

Signed-off-by: hlts2 <[email protected]>

internal/log/log_test.go

@@ -30,6 +30,7 @@ import (
 )
 
 var (
+	// Goreaine leak is detected by `fastime`, but it should be ignored in the test because it is an external package.
 	goleakIgnoreOptions = []goleak.Option{
 		goleak.IgnoreTopFunction("github.com/kpango/fastime.(*Fastime).StartTimerD.func1"),
 	}