first write to .new then move after finishing writing to prevent data corruption

core/core.go

@@ -63,16 +63,21 @@ func Init(dataPath string) error {
 }
 
 func (d *FullData) WriteJSON(dataPath string) error {
-	d.Lock()
+	// use .new so if there's a corruption when writing the old file is intact
+	path := filepath.Join(dataPath, "comitium.json.new")
+
+	d.RLock()
 	jsonBytes, err := json.MarshalIndent(&d, "", "\t")
-	d.Unlock()
+	d.RUnlock()
 	if err != nil {
 		return err
 	}
-	err = ioutil.WriteFile(filepath.Join(dataPath, "comitium.json"), jsonBytes, 0666)
+	err = ioutil.WriteFile(path, jsonBytes, 0666)
 	if err != nil {
 		return err
 	}
 
-	return nil
+	// if full write was successful then overwrite original
+	err = os.Rename(path, filepath.Join(dataPath, "comitium.json"))
+	return err
 }