Go Concurrency: Why Does My Program Print Unexpected Output When Using Channels?

Go Concurrency and Channel Confusion Resolved

When working with concurrency in Go, channels play a pivotal role in communication between goroutines. However, their behavior can sometimes lead to confusion.

Consider the following Go program:

<code class="go">package main

import "fmt"

func display(msg string, c chan bool) {
    fmt.Println("display first message:", msg)
    c <p>The intended behavior is for the program to print "display first message: hello" and then exit. However, the actual output includes the result of the sum function:</p>
<pre class="brush:php;toolbar:false">display first message: hello
10000000000

Explanation

The confusion arises from the fact that the main goroutine blocks on the line:

<code class="go"><p>This means that the main goroutine cannot continue execution until it receives a value from channel c. Both display and sum send a true value to c, which unblocks the main goroutine. However, the scheduler can choose which goroutine to run first.</p>
<p>Possible Execution Order:</p>
<ol>
<li>Main creates two goroutines for display and sum.</li>
<li>The scheduler runs display first, which prints the message and blocks on the channel send.</li>
<li>The scheduler switches to the sum goroutine.</li>
<li>Sum calculates and prints the result.</li>
<li>The scheduler resumes display, which sends a value to the channel.</li>
<li>The main goroutine receives the value and exits.</li>
</ol>
<p><strong>Solution</strong></p>
<p>To ensure that the program prints only the first result, we can use a result channel:</p>
<pre class="brush:php;toolbar:false"><code class="go">func display(msg string, result chan string) {
    result <p>And change the main function to:</p>
<pre class="brush:php;toolbar:false"><code class="go">func main() {
    result := make(chan string)

    go display("hello", result)
    fmt.Println(</code>

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