Alex Rodin

https://github.com/PavelDoGreat/WebGL-Fluid-Simulation/issues/26

https://github.com/PavelDoGreat/WebGL-Fluid-Simulation/issues/18

https://github.com/PavelDoGreat/WebGL-Fluid-Simulation/issues/9

```lua self:Publish("my.topic", Payload) local messages = self:Consume("my.topic") ```

fix https://github.com/antonmedv/expr/issues/217

I couldn't identify the relationship of exprgen with FetchFn.

Maybe this PR will answer https://github.com/antonmedv/expr/pull/254