mod: redirect stderr of executed command for serve to log file

internal/serve/serve.go

@@ -56,6 +56,11 @@ func setupSshServer(host string, port string, host_key_path string, users map[st
 			func(next ssh.Handler) ssh.Handler {
 				return func(s ssh.Session) {
 					cmd := wish.Command(s, name, args...)
+					file, err := os.OpenFile("log", os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600)
+					if err != nil {
+						wish.Fatalf(s, "Could not create or open log file. err: %w", err)
+					}
+					cmd.SetStderr(file)
 					if err := cmd.Run(); err != nil {
 						wish.Fatalln(s, err)
 					}