future-blog-post-18

client5.go

func main() {
    c, _ := context.WithTimeout(context.Background(), 1*time.Second)
    a := 10
    f := future.NewWithContext(c, func() (interface{}, error) {
        return doSomethingThatTakesAWhile(a)
    }).Then(func(v interface{}) (interface{}, error) {
        return doAnotherThing(v.(int))
    })

    val, err := f.Get()
    fmt.Println(val, err, f.IsCancelled())
    
    c, _ = context.WithTimeout(context.Background(), 3*time.Second)
    g := future.NewWithContext(c, func() (interface{}, error) {
        return doSomethingThatTakesAWhile(a)
    }).Then(func(v interface{}) (interface{}, error) {
        return doAnotherThing(v.(int))
    })
    
    val2, err2 := g.Get()
    fmt.Println(val2, err2, g.IsCancelled())

    // once done happens, IsCancelled will never return true
    // and Get still has the calculated values
    time.Sleep(2 * time.Second)
    val2, err2 = g.Get()
    fmt.Println(val2, err2, g.IsCancelled())
}