Number of goroutines

Learn to launch many goroutines and concurrency.

Many goroutines

Starting many goroutines in Go is easy: write go f(i) in a loop. Each runs independently and the scheduler spreads them across cores.

Hundreds of thousands of goroutines can live at once; the memory cost is in kilobytes. This is the key trait that separates goroutines from OS threads.

But if goroutines access shared data a data race occurs. You must protect it with sync.Mutex or a channel. go test -race detects races.

Goroutine cost

A goroutine starts with about 2 KB of stack. When it fills Go doubles it automatically (growing stack). This avoids memory issues even with deep recursion.

Comparison: a Linux thread reserves 8 MB of stack. 100k threads need 800 GB; 100k goroutines run with about 200 MB.

This efficiency makes Go a top choice for concurrent server programs.

Exercise Launch many goroutines

Inside main, add a go work() call inside a loop and print many started with fmt.Println.

Show example solution

package main

import "fmt"

func work() {
    fmt.Println("çoklu başladı")
}

func main() {
    for i := 0; i < 3; i++ {
        go work()
    }
    fmt.Println("çoklu başladı")
}

Test yourself

How is a data race detected?
- go run -v
- go vet
- go build -race
- go test -race
Show answer

go test -race — go vet does static analysis, not race detection.

Goroutine stack size

A goroutine starts with about ____ of stack.

Show answer

A goroutine starts with about 2 KB of stack.

Match cost concepts

goroutine

2 KB
OS thread

8 MB
growing stack

Auto-grows
data race

Race

Next lesson: Summary - Goroutines

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