public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
}

private readonly IHttpContextAccessor _httpContextAccessor;

public HomeController(IHttpContextAccessor httpContextAccessor){
　　_httpContextAccessor = httpContextAccessor;  
}

public object get(){
　　return _httpContextAccessor.HttpContext.Connection.RemoteIpAddress.MapToIPv4().ToString();
}