[BUG] panic concurrent map read and map write

Describe the bug

fatal error: concurrent map read and map write

goroutine 28 [running]: runtime.throw({0x75b602, 0x6edb80}) /usr/local/go/src/runtime/panic.go:1198 +0x71 fp=0xc00015ae10 sp=0xc00015ade0 pc=0x434991 runtime.mapaccess1(0x6fee40, 0xc000179170, 0xa3a700) /usr/local/go/src/runtime/map.go:411 +0x1f7 fp=0xc00015ae50 sp=0xc00015ae10 pc=0x40f737 github.com/amir-the-h/okex/api/ws.(ClientWs).sender(0xc00032c000, 0x0) /go/pkg/mod/github.com/amir-the-h/okex@v1.1.4-alpha/api/ws/client.go:282 +0x212 fp=0xc00015af88 sp=0xc00015ae50 pc=0x6bf992 github.com/amir-the-h/okex/api/ws.(ClientWs).dial.func2() /go/pkg/mod/github.com/amir-the-h/okex@v1.1.4-alpha/api/ws/client.go:245 +0x25 fp=0xc00015afe0 sp=0xc00015af88 pc=0x6bf645 runtime.goexit() /usr/local/go/src/runtime/asm_amd64.s:1581 +0x1 fp=0xc00015afe8 sp=0xc00015afe0 pc=0x463ee1 created by github.com/amir-the-h/okex/api/ws.(*ClientWs).dial /go/pkg/mod/github.com/amir-the-h/okex@v1.1.4-alpha/api/ws/client.go:244 +0x29f

To Reproduce

Occasionally happened
Sample code for usage scenarios as follows

cli := ws.NewClient() ch := make(chan *pub.MarkPrice) // subscribe mark price channel cli.Public.MarkPrice(req, ch)

for {

    select {
    case mark:= <- ch:
        //
        handlePrice(mark)
        ticker.Reset(time.Minute)
    case <-ticker.C:
        // ticker triggered, the websocket may be broken, try reconnect
        cli.Cancel()
        cli = ws.NewClient()
                    // resubscribe
        cli.Public.MarkPrice(req, ch)
    }
}



**Expected behavior**
no panic

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Desktop (please complete the following information):**
 - Device: [e.g Macbook Pro]
 - OS: [e.g. MacOS]
 - Version [e.g. 14.1]

happened in macos and ubuntu

**Golang (please complete the following information):**
 - Version: 1.17

**Additional context**
Add any other context about the problem here.

amir-the-h / okex

[BUG] panic concurrent map read and map write #31