Shared and race conditions

[Kagamin]

On Wednesday, 29 November 2017 at 16:13:13 UTC, Wanderer wrote:
> static void getId(shared IdGen!(MyId)* g)
> {
>     writeln("next: ", g.next());
>     writeln("next: ", g.next());
> }

writeln synchronizes on stdout, so your code is mostly 
serialized, good example of a very subtle race condition.