When stopping, close the database (#1686)

* When stopping, close the database

This patch is likely to cause errornous behavior in the application.
This is due to the fact that the application doesn't gracefully shut
down, but is forcefully terminated.

However, the purpose is to uncover what needs to be done, to make
it a more graceful shutdown.

pkg/database/database.go

@@ -89,6 +89,13 @@ func Initialize(databasePath string) error {
 	return nil
 }
 
+func Close() error {
+	WriteMu.Lock()
+	defer WriteMu.Unlock()
+
+	return DB.Close()
+}
+
 func open(databasePath string, disableForeignKeys bool) *sqlx.DB {
 	// https://github.com/mattn/go-sqlite3
 	url := "file:" + databasePath + "?_journal=WAL"