asyncprocimpl: proc runGetOutputStream(sh: ProcArgs; cmd: seq[string];
                   prefixCmd = none(seq[string]); toAdd: set[ProcOption] = {};
                   toRemove: set[ProcOption] = {}; input = none(AsyncIoBase);
                   output = none(AsyncIoBase); outputErr = none(AsyncIoBase);
                   env = none(ProcEnv); envModifier = none(ProcEnv);
                   workingDir = none(string); processName = none(string);
                   logFn = none(LogFn); onErrorFn = none(OnErro