Ensure the proxy doesn't shut down too early if stdin is EOF.

proxy/src/main/java/com/velocitypowered/proxy/Velocity.java

@@ -45,5 +45,10 @@ public class Velocity {
     double bootTime = (System.currentTimeMillis() - startTime) / 1000d;
     logger.info("Done ({}s)!", new DecimalFormat("#.##").format(bootTime));
     server.getConsoleCommandSource().start();
+
+    // If we don't have a console available (because SimpleTerminalConsole returned), then we still
+    // need to wait, otherwise the JVM will reap us as no non-daemon threads will be active once the
+    // main thread exits.
+    server.awaitProxyShutdown();
   }
 }

proxy/src/main/java/com/velocitypowered/proxy/VelocityServer.java

@@ -138,6 +138,10 @@ public class VelocityServer implements ProxyServer {
     return commandManager;
   }
 
+  void awaitProxyShutdown() {
+    cm.getBossGroup().terminationFuture().syncUninterruptibly();
+  }
+
   @EnsuresNonNull({"serverKeyPair", "servers", "pluginManager", "eventManager", "scheduler",
       "console", "cm", "configuration"})
   void start() {

proxy/src/main/java/com/velocitypowered/proxy/network/ConnectionManager.java

@@ -160,6 +160,10 @@ public final class ConnectionManager {
     }
   }
 
+  public EventLoopGroup getBossGroup() {
+    return bossGroup;
+  }
+
   public ServerChannelInitializerHolder getServerChannelInitializer() {
     return this.serverChannelInitializer;
   }