The "go" method of Debugger classes in Dexter used to be called once, to launch the process. However with the new DebuggerController classes it's now used to set the target process free running until we hit a relevant source line. Alas, I'd baked the former assumption into the DbgEng driver and had the "go" method do nothing. This can lead to an infinite loop where the DebuggerController repeatedly calls "go".
Quickly experimenting with setting the target process free running under DbgEng shows some weird behaviour which I'm yet to get to the bottom of; in the meantime, have the "go" method single step instead. This is slow, but makes progress.
Tests: this is stimulated by the tests in D91648