Go Select and Channels Simple Select Working with Channels
Example
In this example we create a goroutine (a function running in a separate thread) that accepts a chan parameter, and simply loops, sending information into the channel each time.
In the main we have a for loop and a select. The select will block processing until one of the case statements becomes true. Here we have declared two cases; the first is when information comes through the channel, and the other is if no other case occurs, which is known as default.
// Use of the select statement with channels (no timeouts)
package main
import (
"fmt"
"time"
)
// Function that is "chatty"
// Takes a single parameter a channel to send messages down
func chatter(chatChannel chan<- string) {
// Clean up our channel when we are done.
// The channel writer should always be the one to close a channel.
defer close(chatChannel)
// loop five times and die
for i := 1; i <= 5; i++ {
time.Sleep(2 * time.Second) // sleep for 2 seconds
chatChannel <- fmt.Sprintf("This is pass number %d of chatter", i)
}
}
// Our main function
func main() {
// Create the channel
chatChannel := make(chan string, 1)
// start a go routine with chatter (separate, non blocking)
go chatter(chatChannel)
// This for loop keeps things going while the chatter is sleeping
for {
// select statement will block this thread until one of the two conditions below is met
// because we have a default, we will hit default any time the chatter isn't chatting
select {
// anytime the chatter chats, we'll catch it and output it
case spam, ok := <-chatChannel:
// Print the string from the channel, unless the channel is closed
// and we're out of data, in which case exit.
if ok {
fmt.Println(spam)
} else {
fmt.Println("Channel closed, exiting!")
return
}
default:
// print a line, then sleep for 1 second.
fmt.Println("Nothing happened this second.")
time.Sleep(1 * time.Second)
}
}
}
