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Cover image for Go Course: Select
Karan Pratap Singh
Karan Pratap Singh

Posted on • Originally published at karanpratapsingh.com

Go Course: Select

In this tutorial, we will learn about the select statement in Go.

The select statement blocks the code and waits for multiple channel operations simultaneously.

A select blocks until one of its cases can run, then it executes that case. It chooses one at random if multiple are ready.

package main

import (
    "fmt"
    "time"
)

func main() {
    one := make(chan string)
    two := make(chan string)

    go func() {
        time.Sleep(time.Second * 2)
        one <- "One"
    }()

    go func() {
        time.Sleep(time.Second * 1)
        two <- "Two"
    }()

    select {
    case result := <-one:
        fmt.Println("Received:", result)
    case result := <-two:
        fmt.Println("Received:", result)
    }

    close(one)
    close(two)
}
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Similar to switch , select also has a default case that runs if no other case is ready. This will help us send or receive without blocking.

func main() {
    one := make(chan string)
    two := make(chan string)

    for x := 0; x < 10; x++ {
        go func() {
            time.Sleep(time.Second * 2)
            one <- "One"
        }()

        go func() {
            time.Sleep(time.Second * 1)
            two <- "Two"
        }()
    }

    for x := 0; x < 10; x++ {
        select {
        case result := <-one:
            fmt.Println("Received:", result)
        case result := <-two:
            fmt.Println("Received:", result)
        default:
            fmt.Println("Default...")
            time.Sleep(200 * time.Millisecond)
        }
    }

    close(one)
    close(two)
}
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It's also important to know that an empty select {} blocks forever.

func main() {
    ...
    select {}

    close(one)
    close(two)
}
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This article is part of my open source Go Course available on Github.

GitHub logo karanpratapsingh / learn-go

Master the fundamentals and advanced features of the Go programming language

Learn Go

Hey, welcome to the course, and thanks for learning Go. I hope this course provides a great learning experience.

This course is also available on my website and as an ebook on leanpub. Please leave a ⭐ as motivation if this was helpful!

Table of contents

What is Go?

Go (also known as Golang) is a programming language developed at Google in 2007 and open-sourced in 2009.

It focuses on simplicity, reliability, and efficiency. It was designed to combine the efficacy, speed…




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