Closing a channel

Learn to close a channel with close and detect closure.

Closing a channel

You close a channel with close(ch). Sending on a closed channel panics; receiving from a closed channel returns the zero value. This is how you signal that no more data will come.

With v, ok := <-ch you learn if the channel is open. If ok is false the channel is closed and drained. The for v := range ch loop ends automatically when the channel closes.

close and range

Closing a channel pairs with for v := range ch. The sender calls close(ch) after all data is sent; the receiver's range loop ends automatically.

The sender, not the receiver, should close the channel; if the receiver closes it the sender may panic. Following this principle is key for safe concurrency.

Exercise Close a channel and print

Inside main, add a make(chan string) call and print closed with fmt.Println.

Show example solution

package main

import "fmt"

func main() {
    ch := make(chan string, 1)
    ch <- "kapatıldı"
    close(ch)
    fmt.Println(<-ch)
}

Test yourself

What happens when you send on a closed channel?
- Silently ignored
- It panics
- It blocks
- Returns zero value
Show answer

It panics — it panics. RECEIVING from a closed channel returns zero value.

Closing a channel

ch := make(chan int, 2)
ch <- 1
ch <- 2
____
for v := range ch {
    fmt.Println(v)
}

Show answer

ch := make(chan int, 2)
ch <- 1
ch <- 2
close(ch)
for v := range ch {
    fmt.Println(v)
}

Match close concepts

close(ch)

Close
v, ok

Status
range

Auto-end
panic

Send on closed

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