Auto-close DB and fix server closing algorithm

src/main/java/net/pixtaded/crab/server/CrabServer.java

@@ -60,9 +60,9 @@ public class CrabServer implements Crab {
         }
     }
 
-    public void stop() {
-        try {
+    public synchronized void stop() {
         isStopped = true;
+        try {
             if (socket != null) socket.close();
             if (serverSocket != null) serverSocket.close();
         } catch (IOException e) {

src/main/java/net/pixtaded/crab/server/Database.java

@@ -6,7 +6,7 @@ import java.sql.*;
 import java.util.Date;
 import java.util.Locale;
 
-public class Database {
+public class Database implements AutoCloseable {
 
     private Connection connection;
     private String logs = "";
@@ -68,4 +68,10 @@ public class Database {
         else return logs.getBytes().length;
     }
 
+    @Override
+    public void close() throws SQLException {
+        if (connection != null && !connection.isClosed()) {
+            connection.close();
+        }
+    }
 }