Goroutines and channel coordination

The idea

Enter with functions and blocking operations understood. A go statement starts a goroutine that can execute concurrently with its caller. Its execution order relative to other goroutines is not a reliable basis for program logic. The process exits when main returns, so background work needs explicit coordination if its result matters. Avoid using a delay as a substitute for a completion contract.

A channel transports typed values between goroutines. With an unbuffered channel, a send and a matching receive coordinate with one another; the send cannot complete without a receiver. The example has one producer and one receive, making its printed value deterministic despite flexible scheduling. Larger designs need ownership of channel closing and cancellation behavior. A receiver should not close a channel while a producer may still send to it.

package main
import "fmt"
func main(){
 result:=make(chan int)
 go func(){result<-6*7}()
 fmt.Println(<-result)
}

42

Main waits for the received value before printing and returning. The producer’s calculation is independent of scheduling order.