How to syntactically prevent a reader from closing a channel?

In Go, you cannot directly prevent closing a channel because the close operator works with the channel, not its type. However, you can syntactically restrict access to closing the channel by passing the channel as read-only (<-chan T) in parts of the code where closing is not needed.

A channel in Go has three main types:

• chan T — bidirectional channel (read and write)
• <-chan T — read-only channel
• chan<- T — write-only channel

Only the owner with a chan T can close the channel. If a function accepts <-chan T, it cannot close the channel because the close operator requires chan T.

Example:

func producer(ch chan<- int) {
    for i := 0; i < 5; i++ {
        ch <- i
    }
    // Only the owner with chan T can close the channel
}

func consumer(ch <-chan int) {
    for v := range ch {
        fmt.Println(v)
    }
    // Cannot call close(ch) here because ch is read-only
}

func main() {
    ch := make(chan int)
    go producer(ch)
    consumer(ch)
}

Thus, to prevent the reader from closing the channel, pass it as <-chan T. Only the owner with chan T can close the channel.