Go Gin middleware events - go

Question

I'm trying to make middleware for the Gin server to handle events during a single request because I need things like IP address from context and to not pass the whole context I'd rather pass my listener which makes my method not dependent on gin.Context.
I set up a server
func main() {
router := gin.New()
router.Use(gin.Recovery())
api := router.Group("api", middleware())
{
api.GET("test/:id", endpoint)
}
router.Run("localhost:8080")
}
and made a middleware
func middleware() gin.HandlerFunc {
return func(c *gin.Context) {
listener := make(chan int)
c.Set("EventListener", listener)
go func() {
select {
case <-listener:
fmt.Println("event called")
default:
fmt.Println("default")
}
}()
c.Next()
}
}
then I got an endpoint where I get my listener and then pass it to any function I want to
func endpoint(c *gin.Context) {
listener := c.MustGet("EventListener").(chan int)
id := c.Param("id")
idInt, err := strconv.ParseInt(id, 10, 64)
if err != nil {
fmt.Println(err)
return
}
doSomething(listener, int(idInt))
}
and doSomething function to show that no context is used later on
func doSomething(listener chan int, id int) {
if id == 1 {
fmt.Println("ERROR: cause event and exit")
listener <- int(id)
return
}
if id == 2 {
fmt.Println("WARN: cause event but continue")
listener <- int(id)
}
fmt.Println("OK: everything is fine")
}
And the way it works now is:
when you call GET http://localhost:8080/api/test/1 it will trigger event and exit
when you call GET http://localhost:8080/api/test/2 it will trigger event and keep working
when you call GET http://localhost:8080/api/test/3 it will not trigger event because all is ok.
So everything is working but only for one event along request. You can not call another one, because select already passed so my question is how to fix it and allow to trigger event multiple times.
I know I can make it like
for {
select {
case <-listener:
fmt.Println("event called")
}
}
but what would be stop condition of this loop?
I know there is something like c.Done() which is chan but have no idea how to use it in my case because I can make it like
for {
select {
case <-listener:
fmt.Println("event called")
case <-c.Done():
return
}
}
but how to pass that c.Done()? This goroutine does not stop.

Answer 1

I found out that there is also c.Request.Context().Done() which works now, stopping goroutine and allowing to handle multiple events
go func() {
for {
select {
case <-listener:
fmt.Println("event called")
case <-c.Request.Context().Done():
return
}
}
}()