How to add connection request headers in SignalR Core JS client?

In my SignalR Hub (.NET 5) i want to override the OnConnectedAsync method to read the request headers that the client sent using:

public override Task OnConnectedAsync() {
    var username = Context.GetHttpContext().Request.Headers["username"];
    return base.OnConnectedAsync();
}

How do i build the connection to my hub using the @microsoft/signalr client library? Currently my connection looks like this:

var connection = new signalR.HubConnectionBuilder()
    .withUrl("/game")
    // Add username header to connection
    .build();

If I am using the wrong strategy on my server hub, how else would i try to do this?