fix write on closed chan error

README.md

@@ -30,7 +30,7 @@ Standalone binary can be download from one of the following addresses
 | Branch | Source | Address |
 |--------|--------|---------|
 | stable | equinox| <https://dl.equinox.io/shengxiang/gosuv/stable> |
-| stable | github | stable | <https://github.com/codeskyblue/gosuv/releases/latest>|
+| stable | github | <https://github.com/codeskyblue/gosuv/releases/latest>|
 | dev    | equinox| <https://dl.equinox.io/shengxiang/gosuv/dev> |
 
 Or if you have go enviroment, you can also build from source.

broadcast.go

@@ -124,9 +124,12 @@ func NopWriteCloser(w io.Writer) io.WriteCloser {
 type chanStrWriter struct {
 	C      chan string
 	closed bool
+	mu     sync.Mutex
 }
 
 func (c *chanStrWriter) Write(data []byte) (n int, err error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
 	if c.closed {
 		return 0, errors.New("chan writer closed")
 	}
@@ -135,6 +138,8 @@ func (c *chanStrWriter) Write(data []byte) (n int, err error) {
 }
 
 func (c *chanStrWriter) Close() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
 	if !c.closed {
 		c.closed = true
 		close(c.C)