Wait until all tiles are written out or are cancelled.

cmd/mtwebmapper/tilesupdater.go

@@ -400,26 +400,30 @@ func (tu *tileUpdater) updateBaseTiles(
 	update common.BaseTileUpdateFunc) {
 
 	type jobWriter struct {
-		job *xzc
+		canceled *bool
 		wFn      func() (bool, error)
 	}
 
 	jWs := make(chan jobWriter)
 
+	asyncWrite := make(chan struct{})
+
 	go func() {
+		defer close(asyncWrite)
+
 		for jw := range jWs {
 			updated, err := jw.wFn()
 			if err != nil {
+				*jw.canceled = true
 				log.Printf("WARN: writing tile failed: %v.\n", err)
 			}
 			if !updated {
-				jw.job.canceled = true
+				*jw.canceled = true
 			}
 		}
 	}()
 
 	defer func() {
-		close(jWs)
 		btc.Close()
 		done.Done()
 	}()
@@ -431,6 +435,13 @@ func (tu *tileUpdater) updateBaseTiles(
 			job.canceled = true
 			continue
 		}
-		jWs <- jobWriter{job, btc.WriteFunc(int(job.X), int(job.Z), update)}
+		jWs <- jobWriter{
+			&job.canceled,
+			btc.WriteFunc(int(job.X), int(job.Z), update),
 		}
 	}
+
+	close(jWs)
+	// Wait until all tiles are written.
+	<-asyncWrite
+}