How to Cancel a Goroutine in Go

The example below shows how to cancel a goroutine while is in the middle of executing a long-running task.

package main

import (
    "context"
    "fmt"
    "time"
)

func main() {
    busyChan := make(chan bool)

    ctx, cancel := context.WithCancel(context.Background())
    go func(ctx context.Context) {
        for {
            select {
            case <-busyChan:
                fmt.Println("Pretending to be very busy")
                time.Sleep(5000 * time.Second)
            case <-ctx.Done():
                return
            }
        }
    }(ctx)
    busyChan <- true
    fmt.Println("Doing some other things")
    time.Sleep(3 * time.Second)
    fmt.Println("Stopping the goroutine")
    cancel()
}

Output:

Prentending to be very busy
Doing some other things
Stopping the goroutine