fix: open log file in append mode

src/auth.c

@@ -325,7 +325,6 @@ HEART_BEAT_START:
 int exit_auth(void)
 {
     fprintf(drcom_config.log_file, "gdut-drcom heart-beat exiting!\r\n");
-    fclose(drcom_config.log_file);
     drcom_config.exit = 1;
     return 0;
 }

src/config.c

@@ -51,7 +51,7 @@ void get_version(char* version)
 
 void set_log_file(char * log_file, int len)
 {
-    FILE * logp = fopen(log_file, "w");
+    FILE * logp = fopen(log_file, "a");
     if (logp)
     {
         drcom_config.log_file = logp;