Multiple goroutines in Golang

In this post, we will see how to work with multiple goroutines. If you are looking for the basics, please go through Goroutines in Golang and Channels in Golang.

Multiple Goroutines Simple Example

This code shows how two goroutines will interact when running concurrently. The output order will not be maintained and each time this program is run it may produce a completely new output.

package main

import (
	"fmt"
	"time"
)

func f(s string) {
	for _, c := range s {
		fmt.Print(string(c), " ")
		time.Sleep(10 * time.Millisecond)
	}
}

func main() {
	// run two different goroutine
	go f("Hello")
	go f("World")

	// sleep main goroutine
	time.Sleep(1 * time.Second)
}

The output is as expected and will look like this.

Go Multiple Goroutine

Nested Goroutines

Now we will see what happens if we nest two goroutines. Goroutines can be nested to an arbitrary depth and the output will be even more random in many cases. Here is an example.

package main

import (
	"fmt"
	"time"
)

func g(v int) {
	fmt.Print(v*2, v*v, " ")
}

func SpawnGoroutines(n int) {
	for i := 0; i < n; i++ {
		go g(i)
	}
}

func main() {

	go SpawnGoroutines(10)

	// sleep main goroutine
	time.Sleep(1 * time.Second)
}

Go Nested Goroutines

Communication through Channels

Goroutines can communicate via channels. It is a conduit that helps pass information between two goroutines. Here is an example.

package main

import (
	"fmt"
	"time"
)

func f(ch chan int) {
	for i := 0; i < 10; i++ {
		// send data to the channel
		ch <- i
	}

	// close the channel
	close(ch)
}

func g(ch chan int) {
	// loop over the data from the channel
	for v := range ch {
		fmt.Print(v, " ")
	}
}

func main() {
	ch := make(chan int)

	// send data to the channel
	go f(ch)

	// receive from the channel
	go g(ch)

	// sleep main goroutine
	time.Sleep(1 * time.Second)
}

Go Goroutine Channels

As it can be seen channels are the way multiple goroutines communicate.