Handle net.Error Temporary() deprecation

See https://go.dev/issue/45729.

- Remove hideTempError

  The hideTempError function was used to prevent connection methods from
  returning a net.Error with Temporary() == true.

  Connection methods do not support retry after returning any net.Error,
  including errors with Temporary() == true.

  Presumably hideTempError was used to prevent applications from
  futilely retrying connection method calls on temporary errors.

  The hideTempError function is not needed now that net.Error
  Temporary() is deprecated.

- Remove use of the deprecated net.Error Temporary() method in the
  default ping handler by ignoring all errors returned from
  WriteControl. Ignoring errors allows the application to continue
  reading messages after a write error and is consistent with how the
  default close handler calls WriteControl.

conn.go

@@ -192,13 +192,6 @@ func newMaskKey() [4]byte {
 	return k
 }
 
-func hideTempErr(err error) error {
-	if e, ok := err.(net.Error); ok && e.Temporary() {
-		err = &netError{msg: e.Error(), timeout: e.Timeout()}
-	}
-	return err
-}
-
 func isControl(frameType int) bool {
 	return frameType == CloseMessage || frameType == PingMessage || frameType == PongMessage
 }
@@ -364,7 +357,6 @@ func (c *Conn) RemoteAddr() net.Addr {
 // Write methods
 
 func (c *Conn) writeFatal(err error) error {
-	err = hideTempErr(err)
 	c.writeErrMu.Lock()
 	if c.writeErr == nil {
 		c.writeErr = err
@@ -1014,7 +1006,7 @@ func (c *Conn) NextReader() (messageType int, r io.Reader, err error) {
 	for c.readErr == nil {
 		frameType, err := c.advanceFrame()
 		if err != nil {
-			c.readErr = hideTempErr(err)
+			c.readErr = err
 			break
 		}
 
@@ -1054,7 +1046,7 @@ func (r *messageReader) Read(b []byte) (int, error) {
 				b = b[:c.readRemaining]
 			}
 			n, err := c.br.Read(b)
-			c.readErr = hideTempErr(err)
+			c.readErr = err
 			if c.isServer {
 				c.readMaskPos = maskBytes(c.readMaskKey, c.readMaskPos, b[:n])
 			}
@@ -1075,7 +1067,7 @@ func (r *messageReader) Read(b []byte) (int, error) {
 		frameType, err := c.advanceFrame()
 		switch {
 		case err != nil:
-			c.readErr = hideTempErr(err)
+			c.readErr = err
 		case frameType == TextMessage || frameType == BinaryMessage:
 			c.readErr = errors.New("websocket: internal error, unexpected text or binary in Reader")
 		}
@@ -1164,13 +1156,9 @@ func (c *Conn) PingHandler() func(appData string) error {
 func (c *Conn) SetPingHandler(h func(appData string) error) {
 	if h == nil {
 		h = func(message string) error {
-			err := c.WriteControl(PongMessage, []byte(message), time.Now().Add(writeWait))
-			if err == ErrCloseSent {
-				return nil
-			} else if e, ok := err.(net.Error); ok && e.Temporary() {
-				return nil
-			}
-			return err
+			// Make a best effort to send the pong mesage.
+			_ = c.WriteControl(PongMessage, []byte(message), time.Now().Add(writeWait))
+			return nil
 		}
 	}
 	c.handlePing = h