Non-Blocking Channel Operations

Introduction

This lab aims to test your understanding of non-blocking channel operations in Golang. You will be required to implement non-blocking sends, receives, and multi-way selects using the select statement with a default clause.

Non-Blocking Channel Operations

The problem to be solved in this lab is to implement non-blocking channel operations using the select statement with a default clause.

• Implement a non-blocking receive on a channel using the select statement with a default clause.
• Implement a non-blocking send on a channel using the select statement with a default clause.
• Implement a multi-way non-blocking select using the select statement with multiple case clauses and a default clause.

$ go run non-blocking-channel-operations.go
no message received
no message sent
no activity

There is the full code below:

// Basic sends and receives on channels are blocking.
// However, we can use `select` with a `default` clause to
// implement _non-blocking_ sends, receives, and even
// non-blocking multi-way `select`s.

package main

import "fmt"

func main() {
    messages := make(chan string)
    signals := make(chan bool)

    // Here's a non-blocking receive. If a value is
    // available on `messages` then `select` will take
    // the `<-messages` `case` with that value. If not
    // it will immediately take the `default` case.
    select {
    case msg := <-messages:
        fmt.Println("received message", msg)
    default:
        fmt.Println("no message received")
    }

    // A non-blocking send works similarly. Here `msg`
    // cannot be sent to the `messages` channel, because
    // the channel has no buffer and there is no receiver.
    // Therefore the `default` case is selected.
    msg := "hi"
    select {
    case messages <- msg:
        fmt.Println("sent message", msg)
    default:
        fmt.Println("no message sent")
    }

    // We can use multiple `case`s above the `default`
    // clause to implement a multi-way non-blocking
    // select. Here we attempt non-blocking receives
    // on both `messages` and `signals`.
    select {
    case msg := <-messages:
        fmt.Println("received message", msg)
    case sig := <-signals:
        fmt.Println("received signal", sig)
    default:
        fmt.Println("no activity")
    }
}

Summary

In this lab, you learned how to implement non-blocking channel operations using the select statement with a default clause. You implemented a non-blocking receive, a non-blocking send, and a multi-way non-blocking select.