Golang ending (Binance) web service stream using go routine

I'm integrating Binance API into an existing system and while most parts a straight forward, the data streaming API hits my limited understanding of go-routines. I don't believe there is anything special in the golang SDK for Binance, but essentially I only need two functions, one that starts the data stream and processes events with the event handler given as a parameter and a second one that ends the data stream without actually shutting down the client as it would close all other connections. On a previous project, there were two message types for this, but the binance SDK uses an implementation that returns two go channels, one for errors and an another one, I guess from the name, for stopping the data stram.

The code I wrote for starting the data stream looks like this:

func startDataStream(symbol, interval string, wsKlineHandler futures.WsKlineHandler, errHandler futures.ErrHandler) (err error){

	doneC, stopC, err := futures.WsKlineServe(symbol, interval, wsKlineHandler, errHandler)
	if err != nil {
		fmt.Println(err)
		return err
	}

	return nil
}

This works as expected and streams data. A simple test verifies it:

func runWSDataTest() {
    symbol := "BTCUSDT"
	interval := "15m"
	errHandler := func(err error) {fmt.Println(err)}

	wsKlineHandler := func(event *futures.WsKlineEvent) {fmt.Println(event)}

	_ = startDataStream(symbol, interval, wsKlineHandler, errHandler)
}

The thing that is not so clear to me, mainly due to incomplete understanding, really is how do I stop the stream. I think the returned stopC channel can be used to somehow issue a end singnal similar to, say, a sigterm on system level and then the stream should end.

Say, I have a stopDataStream function that takes a symbol as an argument

func stopDataStream(symbol){

}

Let's suppose I start 5 data streams for five symbols and now I want to stop just one of the streams. That begs the question of:

1. How do I track all those stopC channels?

2. Can I use a collection keyed with the symbol, pull the stopC channel, and then just issue a signal to end just that data stream?

3. How do I actually write into the stopC channel from the stop function?

Again, I don't think this is particularly hard, it's just I could not figure it out yet from the docs so any help would be appreciated.

Thank you

(Answer originally written by @Marvin.Hansen)

Turned out, just saving & closing the channel solved it all. I was really surprised how easy this is, but here is the code of the updated functions:

func startDataStream(symbol, interval string, wsKlineHandler futures.WsKlineHandler, errHandler futures.ErrHandler) (err error) {

	_, stopC, err := futures.WsKlineServe(symbol, interval, wsKlineHandler, errHandler)
	if err != nil {
		fmt.Println(err)
		return err
	}
    // just save the stop channel 
	chanMap[symbol] = stopC
	return nil
}

And then, the stop function really becomes embarrassing trivial:

func stopDataStream(symbol string) {
	stopC := chanMap[symbol]  // load the stop channel for the symbol
	close(stopC) // just close it. 
}

Finally, testing it all out:

var (
	chanMap map[string]chan struct{}
)

func runWSDataTest() {
	chanMap = make(map[string]chan struct{})

	symbol := "BTCUSDT"
	interval := "15m"
	errHandler := func(err error) { fmt.Println(err) }
	wsKlineHandler := getKLineHandler()

	println("Start stream")
	_ = startDataStream(symbol, interval, wsKlineHandler, errHandler)

	time.Sleep(3 * time.Second)

	println("Stop stream")
	stopDataStream(symbol)

	time.Sleep(1 * time.Second)
}

This is it.