Reorder fields on worker.Scheduler

This will hopefully fix a segfault under 32bit platforms caused
by unaligned access to 64bit values.

golang/go#23345

worker/worker.go

@@ -26,6 +26,8 @@ func (j JobFunc) Perform() error {
 
 // Scheduler is the entry-point for scheduling jobs to run asynchronously.
 type Scheduler struct {
+	workers int64 // Number of active worker goroutines.
+
 	delay time.Duration // Delay between ticks.
 
 	waiting chan Job // Jobs ready to be performed.
@@ -40,8 +42,6 @@ type Scheduler struct {
 	quit chan struct{} // Closed when shutting down.
 	done chan struct{} // Closed when finished shutting down.
 
-	workers int64 // Number of active worker goroutines.
-
 	logger log.Logger
 
 	// Acceptable time to wait before forcefully quitting when shutting down