opt: redefine AsyncCallback, pass in the error message

Note: this is a breaking change, the existing codebase using AsyncCallback must be updated accordingly.

Fixes #398

connection.go

@@ -219,7 +219,7 @@ func (c *conn) asyncWrite(itf interface{}) (err error) {
 	hook := itf.(*asyncWriteHook)
 	_, err = c.write(hook.data)
 	if hook.callback != nil {
-		_ = hook.callback(c)
+		_ = hook.callback(c, err)
 	}
 	return
 }
@@ -237,7 +237,7 @@ func (c *conn) asyncWritev(itf interface{}) (err error) {
 	hook := itf.(*asyncWritevHook)
 	_, err = c.writev(hook.data)
 	if hook.callback != nil {
-		_ = hook.callback(c)
+		_ = hook.callback(c, err)
 	}
 	return
 }
@@ -438,7 +438,7 @@ func (c *conn) AsyncWrite(buf []byte, callback AsyncCallback) error {
 	if c.isDatagram {
 		defer func() {
 			if callback != nil {
-				_ = callback(nil)
+				_ = callback(nil, nil)
 			}
 		}()
 		return c.sendTo(buf)
@@ -457,7 +457,7 @@ func (c *conn) Wake(callback AsyncCallback) error {
 	return c.loop.poller.UrgentTrigger(func(_ interface{}) (err error) {
 		err = c.loop.wake(c)
 		if callback != nil {
-			_ = callback(c)
+			_ = callback(c, err)
 		}
 		return
 	}, nil)
@@ -467,7 +467,7 @@ func (c *conn) CloseWithCallback(callback AsyncCallback) error {
 	return c.loop.poller.Trigger(func(_ interface{}) (err error) {
 		err = c.loop.closeConn(c, nil)
 		if callback != nil {
-			_ = callback(c)
+			_ = callback(c, err)
 		}
 		return
 	}, nil)

gnet.go

@@ -140,7 +140,7 @@ type Writer interface {
 // AsyncCallback is a callback which will be invoked after the asynchronous functions has finished executing.
 //
 // Note that the parameter gnet.Conn is already released under UDP protocol, thus it's not allowed to be accessed.
-type AsyncCallback func(c Conn) error
+type AsyncCallback func(c Conn, err error) error
 
 // Socket is a set of functions which manipulate the underlying file descriptor of a connection.
 type Socket interface {
@@ -318,13 +318,14 @@ var MaxStreamBufferCap = 64 * 1024 // 64KB
 // Address should use a scheme prefix and be formatted
 // like `tcp://192.168.0.10:9851` or `unix://socket`.
 // Valid network schemes:
-//  tcp   - bind to both IPv4 and IPv6
-//  tcp4  - IPv4
-//  tcp6  - IPv6
-//  udp   - bind to both IPv4 and IPv6
-//  udp4  - IPv4
-//  udp6  - IPv6
-//  unix  - Unix Domain Socket
+//
+//	tcp   - bind to both IPv4 and IPv6
+//	tcp4  - IPv4
+//	tcp6  - IPv6
+//	udp   - bind to both IPv4 and IPv6
+//	udp4  - IPv4
+//	udp6  - IPv6
+//	unix  - Unix Domain Socket
 //
 // The "tcp" network scheme is assumed when one is not specified.
 func Run(eventHandler EventHandler, protoAddr string, opts ...Option) (err error) {

gnet_test.go

@@ -301,13 +301,13 @@ func (s *testServer) OnTraffic(c Conn) (action Action) {
 						bs := make([][]byte, 2)
 						bs[0] = buf.B[:mid]
 						bs[1] = buf.B[mid:]
-						_ = c.AsyncWritev(bs, func(c Conn) error {
-							logging.Debugf("conn=%s done writev", c.RemoteAddr().String())
+						_ = c.AsyncWritev(bs, func(c Conn, err error) error {
+							logging.Debugf("conn=%s done writev: %v", c.RemoteAddr().String(), err)
 							return nil
 						})
 					} else {
-						_ = c.AsyncWrite(buf.Bytes(), func(c Conn) error {
-							logging.Debugf("conn=%s done write", c.RemoteAddr().String())
+						_ = c.AsyncWrite(buf.Bytes(), func(c Conn, err error) error {
+							logging.Debugf("conn=%s done write: %v", c.RemoteAddr().String(), err)
 							return nil
 						})
 					}
@@ -514,8 +514,8 @@ func (t *testWakeConnServer) OnTick() (delay time.Duration, action Action) {
 		return
 	}
 	t.c = <-t.conn
-	_ = t.c.Wake(func(c Conn) error {
-		logging.Debugf("conn=%s done wake", c.RemoteAddr().String())
+	_ = t.c.Wake(func(c Conn, err error) error {
+		logging.Debugf("conn=%s done wake: %v", c.RemoteAddr().String(), err)
 		return nil
 	})
 	delay = time.Millisecond * 100