Styjun

I have a backend (Go server) which services multiple frontends (web pages) and all requests/responses are handled via channels of specific types. Eg, each frontend is associated (on the backend) with a channel where responses are sent (type = chan<- Response).

I have recently implemented a login system where each frontend is associated with a user ID. To keep track of users I have a map:

logins map[chan<- Response]LoginData

Using this I can quickly look up things related to a frontend, such as permissions. This all works fine.

However, to keep things safer and more modular I have moved all the Login stuff to a separate package. This all works except for one gotcha - the logins map is keyed by the type "chan<- Response", but the Response type is defined in my main package and I don't want to expose it to the Login package. (I don't think I could anyway as it would create a circular reference.)

I only want to use the "chan<- Response" as a handle type in the Login package - I don't need to write to that channel from there. I tried converting the channel to an unsafe.Pointer but that is not allowed by the compiler. On the other hand I can't use a pointer to the channel variable (*chan<- Response) as the handle as the channel is stored in several places so the channel variable will have different addresses.

I also tried casting to a different type of chan such as chan int and chan interface but the compiler does not like that. There does not seem to be any way to convert a channel into a "generic" channel.

I really just want the address of the channel's internal data - like you get when you fmt.Printf a channel with %v. The best I can come up with is to use a string like this:

var c chan<- Response = ...
var userID = "steve"
loginKey = fmt.Sprint(c)
Login.Add(loginKey, userID)

I'm not sure this is valid but seems to work, but it seems to me there should be a better way.

On the other hand I can't use a pointer to the channel variable (*chan<- Response) as the handle as the channel is stored in several places so the channel variable will have different addresses.

But this is the only (halfway acceptable solution): Do not pass around a chan Response but a *(chan Response) (adding directions to your likings). Everything else is crap. Best thing to do is hiding this chan Response in a type.