What is a goroutine?

Learn that a goroutine is a lightweight thread.

What is a goroutine?

A goroutine is a lightweight thread managed by the Go runtime. You start one by putting the go keyword before a function call.

Goroutines are far cheaper than OS threads: they start with a few kilobytes and millions can run at once. The Go scheduler spreads them across CPU cores automatically.

Goroutines share the same address space; so you use channels or the sync package to communicate. Direct access to shared memory causes data races.

Goroutine advantages

The biggest advantage of goroutines is cost. An OS thread reserves 1–8 MB of stack; a goroutine starts at 2 KB and grows on demand.

Go's G-M-P model schedules goroutines efficiently: G goroutine, M machine (OS thread), P processor (context). Idle P's steal work.

So hundreds of thousands of goroutines run at once; memory and switching costs stay low.

Exercise Start a goroutine

Inside main, add a go func(){}() call and print goroutine started with fmt.Println.

Show example solution

package main

import "fmt"

func main() {
    go func() {
        fmt.Println("goroutine başladı")
    }()
    fmt.Println("goroutine başladı")
}

Test yourself

Which keyword starts a goroutine?
- async
- go
- thread
- spawn
Show answer

go — the go keyword. async is JavaScript, thread and spawn belong to other languages.

The goroutine keyword

 To run a function in the background, put ____ before the call.

Show answer

 To run a function in the background, put go before the call.

Match goroutine concepts

goroutine

Lightweight thread
go

Start keyword
G-M-P

Scheduler model
scheduler

Dispatcher

Next lesson: The go keyword

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