startup.cs

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }

    app.Use(async (context, func) =>
    {
        if (context.Request.Path.Value == "/hc")
        {
            context.Response.StatusCode = 200;
            context.Response.ContentLength = 2;
            await context.Response.WriteAsync("UP");
        }
        else
        {
            await func.Invoke();
        }
    });

    app.Run(async (context) =>
    {
        await context.Response.WriteAsync("Hello World!");
    });
}