select.go

package main

import (
	"fmt"
	"runtime"
	"time"
)

// GetWebResults test
func GetWebResults(cancel chan bool) {
	// START OMIT
	c := make(chan string)

	go func() {
		for {
			select {
			case <-cancel:
				c <- "cancelled"
				return
			}
		}
	}()

	timeout := time.After(100 * time.Millisecond)
	for {
		select { // HL
		case <-c: // HL
			fmt.Println("returned")
			return
		case <-timeout: // HL
			fmt.Println("timed-out")
			// comment-in either return or cancel channel signal
			// return
			cancel <- true
		}
	}
}

func main() {
	cancel := make(chan bool) // just to simulate case we want to cancel
	GetWebResults(cancel)
	if activeGoroutines := runtime.NumGoroutine(); activeGoroutines != 1 {
		fmt.Printf("program should stop gracefully. num of active go-routines:%v", activeGoroutines)
	}
}

Manual cancellation of go-routine using channel.