fixed bug in golang channel handling (json-rpc mode)

* golang channels are meant to be 1:1 channels, so if multiple
  goroutines listen on the same channel for messages, only one will
  receive the message and the others are not, which lead to lost
  messages.

  In order to fix that, we create a dedicated golang channel for every
  websocket connection.

see #451

src/api/api.go

@@ -390,7 +390,7 @@ func (a *Api) SendV2(c *gin.Context) {
 }
 
 func (a *Api) handleSignalReceive(ws *websocket.Conn, number string, stop chan struct{}) {
-	receiveChannel, err := a.signalClient.GetReceiveChannel()
+	receiveChannel, channelUuid, err := a.signalClient.GetReceiveChannel()
 	if err != nil {
 		log.Error("Couldn't get receive channel: ", err.Error())
 		return
@@ -399,6 +399,7 @@ func (a *Api) handleSignalReceive(ws *websocket.Conn, number string, stop chan s
 	for {
 		select {
 		case <-stop:
+			a.signalClient.RemoveReceiveChannel(channelUuid)
 			ws.Close()
 			return
 		case msg := <-receiveChannel:

src/client/client.go

@@ -730,12 +730,20 @@ func (s *SignalClient) Receive(number string, timeout int64, ignoreAttachments b
 	}
 }
 
-func (s *SignalClient) GetReceiveChannel() (chan JsonRpc2ReceivedMessage, error) {
+func (s *SignalClient) GetReceiveChannel() (chan JsonRpc2ReceivedMessage, string, error) {
 	jsonRpc2Client, err := s.getJsonRpc2Client()
 	if err != nil {
-		return nil, err
+		return nil, "", err
 	}
-	return jsonRpc2Client.GetReceiveChannel(), nil
+	return jsonRpc2Client.GetReceiveChannel()
+}
+
+func (s *SignalClient) RemoveReceiveChannel(channelUuid string) {
+	jsonRpc2Client, err := s.getJsonRpc2Client()
+	if err != nil {
+		return
+	}
+	jsonRpc2Client.RemoveReceiveChannel(channelUuid)
 }
 
 func (s *SignalClient) CreateGroup(number string, name string, members []string, description string, editGroupPermission GroupPermission, addMembersPermission GroupPermission, groupLinkState GroupLinkState) (string, error) {

src/client/jsonrpc2.go

@@ -33,7 +33,7 @@ type JsonRpc2ReceivedMessage struct {
 type JsonRpc2Client struct {
 	conn                     net.Conn
 	receivedResponsesById    map[string]chan JsonRpc2MessageResponse
-	receivedMessages         chan JsonRpc2ReceivedMessage
+	receivedMessagesChannels map[string]chan JsonRpc2ReceivedMessage
 	lastTimeErrorMessageSent time.Time
 	signalCliApiConfig       *utils.SignalCliApiConfig
 	number                   string
@@ -44,6 +44,7 @@ func NewJsonRpc2Client(signalCliApiConfig *utils.SignalCliApiConfig, number stri
 		signalCliApiConfig:       signalCliApiConfig,
 		number:                   number,
 		receivedResponsesById:    make(map[string]chan JsonRpc2MessageResponse),
+		receivedMessagesChannels: make(map[string]chan JsonRpc2ReceivedMessage),
 	}
 }
 
@@ -54,8 +55,6 @@ func (r *JsonRpc2Client) Dial(address string) error {
 		return err
 	}
 
-	r.receivedMessages = make(chan JsonRpc2ReceivedMessage)
-
 	return nil
 }
 
@@ -143,14 +142,16 @@ func (r *JsonRpc2Client) ReceiveData(number string) {
 		var resp1 JsonRpc2ReceivedMessage
 		json.Unmarshal([]byte(str), &resp1)
 		if resp1.Method == "receive" {
+			for _, c := range r.receivedMessagesChannels {
 				select {
-			case r.receivedMessages <- resp1:
+				case c <- resp1:
 					log.Debug("Message sent to golang channel")
 				default:
 					log.Debug("Couldn't send message to golang channel, as there's no receiver")
 				}
 				continue
 			}
+		}
 
 		var resp2 JsonRpc2MessageResponse
 		err = json.Unmarshal([]byte(str), &resp2)
@@ -166,6 +167,19 @@ func (r *JsonRpc2Client) ReceiveData(number string) {
 	}
 }
 
-func (r *JsonRpc2Client) GetReceiveChannel() chan JsonRpc2ReceivedMessage {
+func (r *JsonRpc2Client) GetReceiveChannel() (chan JsonRpc2ReceivedMessage, string, error) {
-	return r.receivedMessages
+	c := make(chan JsonRpc2ReceivedMessage)
+
+	channelUuid, err := uuid.NewV4()
+	if err != nil {
+		return c, "", err
+	}
+
+	r.receivedMessagesChannels[channelUuid.String()] = c
+
+	return c, channelUuid.String(), nil
+}
+
+func (r *JsonRpc2Client) RemoveReceiveChannel(channelUuid string) {
+	delete(r.receivedMessagesChannels, channelUuid)
 }