Synchronization with channels

What channel operations are directly used in the synchronization process?

package main

func main() {
    tasks := make(chan int)    // (1)
    sync := make(chan bool, 1) // (1)

    workers := 2
    done := make(chan bool, workers) // (1)
    for range make([]struct{}, workers) {
        go doWork(tasks, sync, done)
    }

    close(tasks) // (4)

    for workers > 0 {
        <-done // (3)
        workers--
    }
}

func doWork(tasks <-chan int, sync chan bool, done chan<- bool) {
    for range tasks {
        // do work
        sync <- true // (2)
        // access to shared source
        <-sync // (3)
    }

    done <- true // (2)
}