taskworkers can be async or take a callback

src/taskworker.js

@@ -16,7 +16,8 @@ const apptask = require('./apptask.js'),
     safe = require('safetydance'),
     settings = require('./settings.js'),
     tasks = require('./tasks.js'),
-    updater = require('./updater.js');
+    updater = require('./updater.js'),
+    util = require('util');
 
 const TASKS = { // indexed by task type
     app: apptask.run,
@@ -103,7 +104,12 @@ async.series([
     };
 
     try {
-        TASKS[task.type].apply(null, task.args.concat(progressCallback).concat(resultCallback));
+        if (util.types.isAsyncFunction(TASKS[task.type])) { // can also use fn[Symbol.toStringTag]
+            const [error, result] = await safe(TASKS[task.type].apply(null, task.args.concat(progressCallback)));
+            resultCallback(error, result);
+        } else {
+            TASKS[task.type].apply(null, task.args.concat(progressCallback).concat(resultCallback));
+        }
     } catch (error) {
         debug('Uncaught exception in task', error);
         process.exit(1); // do not call setCompleted() intentionally. the task code must be resilient enough to handle it