title: Plugin already initialized
body: <p>I am doing plugin for teleport between servers in bungeecord. Suddenly, i don't know how, but error starts occur. Can you tell me, where is the problem? Thank you for your response.</p>
  
  <p>Full Stacktrace:</p>
  
  <p>org.bukkit.plugin.InvalidPluginException: java.lang.IllegalArgumentException: Plugin already initialized!
          at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:139) ~[spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:334) ~[spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:253) [spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at org.bukkit.craftbukkit.v1_15_R1.CraftServer.loadPlugins(CraftServer.java:351) [spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at net.minecraft.server.v1_15_R1.DedicatedServer.init(DedicatedServer.java:203) [spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at net.minecraft.server.v1_15_R1.MinecraftServer.run(MinecraftServer.java:784) [spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at java.lang.Thread.run(Thread.java:830) [?:?]
  Caused by: java.lang.IllegalArgumentException: Plugin already initialized!
          at org.bukkit.plugin.java.PluginClassLoader.initialize(PluginClassLoader.java:178) ~[spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at org.bukkit.plugin.java.JavaPlugin.(JavaPlugin.java:52) ~[spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at pl.piotrek.main.Main.(Main.java:9) ~[?:?]
          at jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[?:?]
          at jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[?:?]
          at jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:?]
          at java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500) ~[?:?]
          at java.lang.reflect.ReflectAccess.newInstance(ReflectAccess.java:166) ~[?:?]
          at jdk.internal.reflect.ReflectionFactory.newInstance(ReflectionFactory.java:404) ~[?:?]
          at java.lang.Class.newInstance(Class.java:591) ~[?:?]
          at org.bukkit.plugin.java.PluginClassLoader.(PluginClassLoader.java:72) ~[spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:135) ~[spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          ... 6 more
  Caused by: java.lang.IllegalStateException: Initial initialization
          at org.bukkit.plugin.java.PluginClassLoader.initialize(PluginClassLoader.java:181) ~[spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at org.bukkit.plugin.java.JavaPlugin.(JavaPlugin.java:52) ~[spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at pl.piotrek.main.Main.(Main.java:9) ~[?:?]
          at jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[?:?]
          at jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[?:?]
          at jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:?]
          at java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500) ~[?:?]
          at java.lang.reflect.ReflectAccess.newInstance(ReflectAccess.java:166) ~[?:?]
          at jdk.internal.reflect.ReflectionFactory.newInstance(ReflectionFactory.java:404) ~[?:?]
          at java.lang.Class.newInstance(Class.java:591) ~[?:?]
          at org.bukkit.plugin.java.PluginClassLoader.(PluginClassLoader.java:72) ~[spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:135) ~[spigot-1.15.2.jar:git-Spigot-800b93f-8160e29]
          ... 6 more</p>
  
  <p>Main class:</p>
  
  <pre><code>package pl.piotrek.main;
  
  import org.bukkit.plugin.java.JavaPlugin;
  import pl.piotrek.commands.ServersCommand;
  import pl.piotrek.events.ServersGuiListener;
  import pl.piotrek.gui.Gui;
  import pl.piotrek.message.channel.PluginMessagingListener;
  import pl.piotrek.message.command.ConnectCommand;
  
  public class Main extends JavaPlugin {
      private static Main instance;
      public static Main getInstance() { return instance; }
      public void setInstance(Main instance) { Main.instance = instance; }
      public Gui gui;
      @Override
      public void onEnable() {
          System.out.println("Enabled TeleportationUtils v1.0.0");
          setInstance(this);
          registerCommands();
          registerListener();
          this.getServer().getMessenger().registerOutgoingPluginChannel(this, "BungeeCord");
          this.getServer().getMessenger().registerIncomingPluginChannel(this, "BungeeCord", new PluginMessagingListener());
          gui = new Gui();
      }
      public void registerCommands() {
          getCommand("connect").setExecutor(new ConnectCommand());
          getCommand("servers").setExecutor(new ServersCommand());
      }
      public void registerListener() {
          this.getServer().getPluginManager().registerEvents(new ServersGuiListener(), this);
      }
  }
  </code></pre>
  
  <p>Plugin.yml:</p>
  
  <pre><code>name: TeleportationUtils
  version: 1.0.0
  main: pl.piotrek.main.Main
  api-version: 1.15
  commands:
    connect:
      aliases: [cnt]
      description: Connect to another sevrer command
    servers:
      aliases: [svr]
      description: Server menu command for teleport between servers
  permissions:
    commands:
     connect:
  </code></pre>