defer func() {
		if err != nil {
			select {
			case <-c.closed:
				err = c.closeErr
			case <-ctx.Done():
				err = ctx.Err()
			}
			c.close(err)
			err = fmt.Errorf("failed to write frame: %w", err)
		}
	}()

package main

import (
	"context"
	"flag"
	ws "github.com/gorilla/websocket"
	"log"
	"net/http"
	_ "net/http/pprof"
	"nhooyr.io/websocket"
	"sync"
	"time"
)

var (
	concurrency = flag.Int("c", 1, "concurrency")
	wait        = flag.Int("w", 1, "wait milliseconds before close")
)

func startupServer(connWg *sync.WaitGroup) {
	http.HandleFunc("/ws", func(w http.ResponseWriter, r *http.Request) {
		connWg.Add(1)
		defer connWg.Done()
		c, err := websocket.Accept(w, r, &websocket.AcceptOptions{
			InsecureSkipVerify: true,
			CompressionMode:    websocket.CompressionDisabled,
		})
		if err != nil {
			log.Printf("websocket accept error: %v", err)
			return
		}
		var wg sync.WaitGroup
		// uncomment below for resolving the issue
		//wg.Add(1)
		//go func() { // read goroutine
		//	defer wg.Done()
		//	time.Sleep(time.Millisecond * time.Duration(*wait) * 2)
		//	for {
		//		_, _, err := c.Read(context.Background())
		//		if err != nil {
		//			return
		//		}
		//	}
		//}()
		for i := 0; i < *concurrency; i++ { // multi write goroutine
			wg.Add(1)
			go func() {
				defer wg.Done()
				for j := 0; j < 100; j++ {
					// NOTICE background may block forever
					if err := c.Write(context.Background(), websocket.MessageText, []byte("hello")); err != nil {
						return
					}
				}
			}()
		}
		wg.Wait() // wait all write goroutine end
		// do some read after write
		for {
			_, _, err := c.Read(context.Background())
			if err != nil {
				return
			}
		}
	})
	go http.ListenAndServe("127.0.0.1:40000", nil)
}

func main() {
	log.SetFlags(log.Lmicroseconds)
	flag.Parse()

	var connWg sync.WaitGroup
	startupServer(&connWg)

	c, _, err := ws.DefaultDialer.Dial("ws://127.0.0.1:40000/ws", nil)
	if err != nil {
		panic(err)
	}
	go func() {
		for {
			_, _, err := c.ReadMessage()
			if err != nil {
				log.Println("client, read error", err)
				return
			}
		}
	}()
	time.Sleep(time.Millisecond * time.Duration(*wait))
	log.Println("client close", c.Close())
	connWg.Wait() // wait for server end
}