Lavalink logs "Connection established" despite connection failing

Created by: aPinat

Summary

The Lavalink extension logs Connection established even when the connection to the Lavalink server fails.

Details

I believe this happens due to WebSocketClient always triggering the Connected event regardless of whether the connection is successful or not. https://github.com/DSharpPlus/DSharpPlus/blob/f65d2e6100e37e1617381c9d9a4696e080f1d98d/DSharpPlus/Net/WebSocket/WebSocketClient.cs#L101

On .NET Core 3.1, D#+ 4.0.0-nightly-00697, Windows 10 2004

Steps to reproduce

Try to connect to a non-existent Lavalink server and check log.

Discord.Ready += async e => Lavalink = await Discord.UseLavalink().ConnectAsync(new LavalinkConfiguration
{
    Password = "youshallnotpass",
    RestEndpoint = new ConnectionEndpoint("localhost", 2333),
    SocketEndpoint = new ConnectionEndpoint("localhost", 2333)
});

Log output:

[2020-05-28 23:13:41 +02:00] [Lavalink] [Info] Connection established
[2020-05-28 23:13:41 +02:00] [DSharpPlus] [Error] An System.AggregateException occurred in READY.
System.AggregateException: Exceptions occured within one or more event handlers. Check InnerExceptions for details. (Unable to connect to the remote server)
 ---> System.Net.WebSockets.WebSocketException (0x80004005): Unable to connect to the remote server
 ---> System.Net.Http.HttpRequestException: No connection could be made because the target machine actively refused it.
 ---> System.Net.Sockets.SocketException (10061): No connection could be made because the target machine actively refused it.
   at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken)