Improve SetXHandler documentation

conn.go

@@ -981,6 +981,15 @@ func (c *Conn) CloseHandler() func(code int, text string) error {
 // The code argument to h is the received close code or CloseNoStatusReceived
 // if the close message is empty. The default close handler sends a close frame
 // back to the peer.
+//
+// The application must read the connection to process close messages as
+// described in the section on Control Frames above.
+//
+// The connection read methods return a CloseError when a close frame is
+// received. Most applications should handle close messages as part of their
+// normal error handling. Applications should only set a close handler when the
+// application must perform some action before sending a close frame back to
+// the peer.
 func (c *Conn) SetCloseHandler(h func(code int, text string) error) {
 	if h == nil {
 		h = func(code int, text string) error {
@@ -1003,6 +1012,9 @@ func (c *Conn) PingHandler() func(appData string) error {
 // SetPingHandler sets the handler for ping messages received from the peer.
 // The appData argument to h is the PING frame application data. The default
 // ping handler sends a pong to the peer.
+//
+// The application must read the connection to process ping messages as
+// described in the section on Control Frames above.
 func (c *Conn) SetPingHandler(h func(appData string) error) {
 	if h == nil {
 		h = func(message string) error {
@@ -1026,6 +1038,9 @@ func (c *Conn) PongHandler() func(appData string) error {
 // SetPongHandler sets the handler for pong messages received from the peer.
 // The appData argument to h is the PONG frame application data. The default
 // pong handler does nothing.
+//
+// The application must read the connection to process ping messages as
+// described in the section on Control Frames above.
 func (c *Conn) SetPongHandler(h func(appData string) error) {
 	if h == nil {
 		h = func(string) error { return nil }