Fix Close race condition

buffer.go

@@ -17,6 +17,7 @@ type (
 		io.Closer
 		dataCh  chan interface{}
 		flushCh chan struct{}
+		closeCh chan struct{}
 		doneCh  chan struct{}
 		options *Options
 	}
@@ -44,19 +45,22 @@ func (buffer *Buffer) Flush() error {
 	}
 }
 
-// Close flushes the buffer and prevents it from being further used. It times
-// out if it cannot be performed in a timely fashion.
-// The buffer must not be used after it has been closed as all further operations will panic.
+// Close flushes the buffer and prevents it from being further used. The buffer
+// cannot be used after it has been closed as all further operations will panic.
 func (buffer *Buffer) Close() error {
-	close(buffer.dataCh)
-	close(buffer.flushCh)
+	close(buffer.closeCh)
 
+	var err error
 	select {
 	case <-buffer.doneCh:
-		return nil
+		err = nil
 	case <-time.After(buffer.options.CloseTimeout):
-		return ErrTimeout
+		err = ErrTimeout
 	}
+
+	close(buffer.dataCh)
+	close(buffer.flushCh)
+	return err
 }
 
 func (buffer *Buffer) consume() {
@@ -75,8 +79,10 @@ func (buffer *Buffer) consume() {
 			mustFlush = count >= len(items)
 		case <-ticker:
 			mustFlush = count > 0
-		case _, open := <-buffer.flushCh:
-			isOpen = open
+		case <-buffer.flushCh:
+			mustFlush = count > 0
+		case <-buffer.closeCh:
+			isOpen = false
 			mustFlush = count > 0
 		}
 
@@ -90,7 +96,7 @@ func (buffer *Buffer) consume() {
 	}
 
 	stopTicker()
-	buffer.doneCh <- struct{}{}
+	close(buffer.doneCh)
 }
 
 func newTicker(interval time.Duration) (<-chan time.Time, func()) {
@@ -124,6 +130,7 @@ func New(opts ...Option) *Buffer {
 	buffer := &Buffer{
 		dataCh:  make(chan interface{}),
 		flushCh: make(chan struct{}),
+		closeCh: make(chan struct{}),
 		doneCh:  make(chan struct{}),
 		options: options,
 	}