startup.cs

public void ConfigureServices(IServiceCollection services)
{
    services.AddAuthentication()
    .AddJwtBearer(options => {
        options.Events = new JwtBearerEvents 
        {
            OnMessageReceived = context => 
            {
                var accessToken = context.Request.Query["access_token"];
                if (string.IsNullOrEmpty(accessToken) == false) {
                    context.Token = accessToken;
                }
                return Task.CompletedTask;
            }
        };
    });

    services.AddMvc();
    services.AddSignalR();
}