select.go

// select
package main

import (
	"fmt"
	"time"
)

/*
Go is select lets you wait on multiple channel operations.
Combining goroutines and channels with select is a
powerful feature of Go.

Each channel will receive a value after some amount of time,
to simulate e.g. blocking RPC operations executing in
concurrent goroutines.

We will use select to await both of these values simultaneously,
printing each one as it arrives.

Note that the total execution time is only ~2 seconds
since both the 1 and 2 second Sleeps execute concurrently.
*/

func select_() {
	c1 := make(chan string)
	c2 := make(chan string)

	go func() {
		time.Sleep(time.Second * 1)
		c1 <- "one"
	}()

	go func() {
		time.Sleep(time.Second * 2)
		c2 <- "two"
	}()

	for i := 0; i < 2; i++ {
		select {
		case msg1 := <-c1:
			fmt.Println("received", msg1)
		case msg2 := <-c2:
			fmt.Println("received", msg2)
		}
	}
}