Does std.net.curl: download have support for callbacks?

[adnan338]

On Thursday, 11 June 2020 at 06:05:09 UTC, adnan338 wrote:
> I would like to set a callback for the `download()` function 
> but I do not seem to find a way to add a callback to the 
> procedure.
>
> [...]

I have also been told that Gtk is not thread safe. What does this 
mean and does it effect me on this scenario?