Introduction

Concurrency is one of Go’s superpowers, enabling developers to run tasks in parallel using goroutines. A goroutine is launched with the go keyword followed by a function call, as shown below:

package main

import (
	"fmt"
	"time"
)

func say(s string) {
	for i := 0; i < 5; i++ {
		time.Sleep(100 * time.Millisecond)
		fmt.Println(s)
	}
}

func main() {
	go say("world")
	say("hello")
}

Go playground link to the example

This simple example prints “hello” and “world” concurrently. However, the Go language specification notes that if a function called in a goroutine returns values, those values are discarded. This raises a question: how can we capture and use return values from a goroutine?