From e6c96cc7c823613b0f29779341605c7b6704cdbb Mon Sep 17 00:00:00 2001
From: ArminEbrahimpour <armin890ebp@gmail.com>
Date: Tue, 9 Jun 2026 13:23:05 +0330
Subject: [PATCH] fix: reset readErrCount on success and lower panic threshold
 to 2

readErrCount was never reset on a successful read, meaning it could
accumulate over a long-lived connection and trigger an unexpected panic.

Lowered threshold from 1000 to 2, which is sufficient to support
applications that check errors on every second read while still
catching tight loop bugs. Panic message now includes the underlying
error to aid debugging.
---
 conn.go      | 11 ++++-------
 conn_test.go | 42 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/conn.go b/conn.go
index 9562ffd4..03ab5233 100644
--- a/conn.go
+++ b/conn.go
@@ -1012,18 +1012,16 @@ func (c *Conn) NextReader() (messageType int, r io.Reader, err error) {
 		c.reader.Close()
 		c.reader = nil
 	}
-
 	c.messageReader = nil
 	c.readLength = 0
-
 	for c.readErr == nil {
 		frameType, err := c.advanceFrame()
 		if err != nil {
 			c.readErr = err
 			break
 		}
-
 		if frameType == TextMessage || frameType == BinaryMessage {
+			c.readErrCount = 0 // resets on success
 			c.messageReader = &messageReader{c}
 			c.reader = c.messageReader
 			if c.readDecompress {
@@ -1032,15 +1030,14 @@ func (c *Conn) NextReader() (messageType int, r io.Reader, err error) {
 			return frameType, c.reader, nil
 		}
 	}
-
 	// Applications that do handle the error returned from this method spin in
 	// tight loop on connection failure. To help application developers detect
 	// this error, panic on repeated reads to the failed connection.
 	c.readErrCount++
-	if c.readErrCount >= 1000 {
-		panic("repeated read on failed websocket connection")
+	if c.readErrCount >= 2 {
+		panic("gorilla/websocket: application did not handle error from NextReader, error: " +
+			c.readErr.Error())
 	}
-
 	return noFrame, nil, c.readErr
 }
 
diff --git a/conn_test.go b/conn_test.go
index 28f5c4a3..5e247514 100644
--- a/conn_test.go
+++ b/conn_test.go
@@ -744,3 +744,45 @@ func TestFailedConnectionReadPanic(t *testing.T) {
 	}
 	t.Fatal("should not get here")
 }
+
+func TestNextReadErrCountResetOnSuccess(t *testing.T) {
+	// setup a pipe to write a real websocket frame
+	r, w := io.Pipe()
+	conn := newTestConn(r, w, false) // client connection
+
+	// simulate accumulated errors from previous failures
+	conn.readErrCount = 1
+
+	// write a valid text frame from another goroutine
+	go func() {
+		serverConn := newTestConn(r, w, true) // server connection
+		serverConn.WriteMessage(TextMessage, []byte("Test"))
+	}()
+
+	// successful read should reset the counter
+	_, _, err := conn.NextReader()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if conn.readErrCount != 0 {
+		t.Errorf("expected readErrCount to be 0 after success, got %d", conn.readErrCount)
+	}
+}
+
+func TestNextReaderPanicsOnSecondFailedRead(t *testing.T) {
+	r, w := io.Pipe()
+	conn := newTestConn(r, w, false) // client connection
+
+	// force the connection into a permanently failed state
+	conn.readErr = errors.New("simulated failure")
+	conn.readErrCount = 1 // already had 1 failed read
+
+	defer func() {
+		r := recover()
+		if r == nil {
+			t.Fatal("expected panic on second read of failed connection, got none")
+		}
+	}()
+
+	conn.NextReader()
+}