runtime.Goexit

Learn to cleanly end a goroutine with Goexit.

runtime.Goexit

runtime.Goexit() ends the calling goroutine but first runs all deferred calls in that goroutine. Other goroutines aren't affected; it isn't a panic and recover doesn't catch it.

go func() {
    defer fmt.Println("temizlik")
    runtime.Goexit()
    fmt.Println("buraya gelinmez")
}()

testing.T.FailNow and t.Fatal stop a test this way.

Goexit, panic and os.Exit

Three different exits: runtime.Goexit ends just this goroutine while running its defers; panic runs defers and, if not recovered, crashes the whole program; os.Exit ends the process immediately without running defers. So if you close resources with defer in main, avoid os.Exit or clean up by hand first.

Exercise Goexit and defer

In a goroutine write defer close(bitti) and defer fmt.Println("temizlik"), then call runtime.Goexit(). main waits with <-bitti and prints "main bitti".

Show example solution

package main

import (
    "fmt"
    "runtime"
)

func main() {
    bitti := make(chan struct{})
    go func() {
        defer close(bitti)
        defer fmt.Println("temizlik")
        runtime.Goexit()
    }()
    <-bitti
    fmt.Println("main bitti")
}

Test yourself

If Goexit is called in the <code>main</code> goroutine and there are no other goroutines, what happens?
- Nothing happens
- The program crashes with a deadlock error
- The program exits normally
- main restarts
Show answer

The program crashes with a deadlock error — Goexit ends main but doesn't exit the program like os.Exit; when no goroutines are left, the runtime reports a deadlock.

End the goroutine

defer wg.Done()
if hata {
    runtime.____()
}

Show answer

defer wg.Done()
if hata {
    runtime.Goexit()
}

Way to exit

runtime.Goexit

This goroutine, defers run
panic

Defers run, program crashes
os.Exit

Defers don't run
return

Normal return

Next lesson: Summary - Runtime

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