just need a space to comment on code :-)

We could Genericise TurtleReaderModule, but that is probably not worth doing right now.
These modules are just designed to make sure that the variables have the same names in each of the implementations of RDF, say Jena, Sesame, Plantain. That helps with consistency. It will break things if you change the Try to a Future for the others. Better just create a TurtleAsyncReaderModule which all async implementations could have in common.