Need a way to detect connection errors of websocket

The error that occurred in stream reading is ignored now.

Lines 91 to 98 in f671bdb

    
           var err error 
        
           buf, err = s.codec.Read(buf[:0]) 
        
           if err != nil { 
        
           	if !s.isClosed() { 
        
           		// log error 
        
           	} 
        
           	return 
        
           }

When we subscribe an event and get no messages, we can not know if the underlying websocket connection is healthy(the network may be down).

Maybe we should add a callback for all unexpected connection errors.

eg.
Subscribe(method string, callback func(b []byte), errHandler func(err error)) (func() error, error)

The proposal sounds okay. Can you share the error you get from the stream?

The proposal sounds okay. Can you share the error you get from the stream?

I subscribed for new heads:

	events := make(chan []byte, 10000)
	closeFn, err = WsRPC.Subscribe("newHeads", func(b []byte) {
		events <- b
	})

Then disable the network, will get a CloseError from gorilla/websocket:
https://github.com/gorilla/websocket/blob/af47554f343b4675b30172ac301638d350db34a5/conn.go#L105

	var err error
	buf, err = s.codec.Read(buf[:0])
	if err != nil {
	if !s.isClosed() {
	// log error
	}
	return
	}