Add mutex around channel close

Signed-off-by: Abhilash Gnan <abhilashgnan@gmail.com>

cmux.go

@@ -114,9 +114,10 @@ type cMux struct {
  root net.Listener
  bufLen int
  errh ErrorHandler
- donec chan struct{}
  sls []matchersListener
  readTimeout time.Duration
+ donec chan struct{}
+ mu sync.Mutex
 }
 
 func matchersToMatchWriters(matchers []Matcher) []MatchWriter {
@@ -139,6 +140,7 @@ func (m *cMux) MatchWithWriters(matchers ...MatchWriter) net.Listener {
  ml := muxListener{
  Listener: m.root,
  connc: make(chan net.Conn, m.bufLen),
+ donec: make(chan struct{}),
  }
  m.sls = append(m.sls, matchersListener{ss: matchers, l: ml})
  return ml
@@ -215,6 +217,9 @@ func (m *cMux) Close() {
 }
 
 func (m *cMux) closeDoneChans() {
+ m.mu.Lock()
+ defer m.mu.Unlock()
+
  select {
  case <-m.donec:
  // Already closed. Don't close again
@@ -262,10 +267,7 @@ func (l muxListener) Accept() (net.Conn, error) {
  return c, nil
  case <-l.donec:
  return nil, ErrServerClosed
- default:
- // do nothing
  }
- return nil, ErrServerClosed
 }
 
 // MuxConn wraps a net.Conn and provides transparent sniffing of connection data.