make sure to shutdown parallel writes for dump-cloud

datatype/keyvalue/rpc.go

@@ -3,6 +3,7 @@ package keyvalue
 import (
 	"context"
 	"fmt"
+	"sync"
 
 	"github.com/janelia-flyem/dvid/datastore"
 	"github.com/janelia-flyem/dvid/dvid"
@@ -82,21 +83,25 @@ func (d *Data) dumpCloud(cmd datastore.Request, reply *datastore.Response) error
 	defer bucket.Close()
 
 	// Start goroutines to write key-value pairs to cloud storage.
+	wg := new(sync.WaitGroup)
 	ch := make(chan *storage.TKeyValue, 1000)
 	for i := 0; i < workers; i++ {
-		go d.writeWorker(bucket, ch)
+		wg.Add(1)
+		go d.writeWorker(wg, bucket, ch)
 	}
 
 	// Send all key-values to the writer goroutines.
 	d.sendKVsToWriters(versionID, ch)
+	close(ch)
+	wg.Wait()
 
 	reply.Output = []byte(fmt.Sprintf("Dumped all key-values to cloud %q for keyvalue %q, uuid %s\n",
 		refStr, d.DataName(), uuidStr))
 	return nil
 }
 
 // writeWorker writes key-value pairs to cloud storage.
-func (d *Data) writeWorker(bucket *blob.Bucket, ch chan *storage.TKeyValue) {
+func (d *Data) writeWorker(wg *sync.WaitGroup, bucket *blob.Bucket, ch chan *storage.TKeyValue) {
 	for kv := range ch {
 		key, err := DecodeTKey(kv.K)
 		if err != nil {
@@ -116,6 +121,7 @@ func (d *Data) writeWorker(bucket *blob.Bucket, ch chan *storage.TKeyValue) {
 			dvid.Errorf("Error closing after key %q to cloud bucket: %v\n", key, err)
 		}
 	}
+	wg.Done()
 }
 
 // iterate through all key-value pairs and send them to the writer channel.