Go by Example: Goroutines

A goroutine is a lightweight thread of execution.
	package main
	import "fmt"
	func f(from string) { for i := 0; i < 3; i++ { fmt.Println(from, ":", i) } }
	func main() {
Suppose we have a function call `f(s)`. Here’s how we’d call that in the usual way, running it synchronously.	f("direct")
To invoke this function in a goroutine, use `go f(s)`. This new goroutine will execute concurrently with the calling one.	go f("goroutine")
You can also start a goroutine for an anonymous function call.	go func(msg string) { fmt.Println(msg) }("going")
Our two function calls are running asynchronously in separate goroutines now, so execution falls through to here. This `Scanln` requires we press a key before the program exits.	fmt.Scanln() fmt.Println("done") }

When we run this program, we see the output of the blocking call first, then the interleaved output of the two goroutines. This interleaving reflects the goroutines being run concurrently by the Go runtime.	$ go run goroutines.go direct : 0 direct : 1 direct : 2 goroutine : 0 going goroutine : 1 goroutine : 2 <enter> done
Next we’ll look at a complement to goroutines in concurrent Go programs: channels.

Next example: Channels.