async

Documentation

Overview

Package async implements a simple Promise API.

Index

• type Promise
  • func (s Promise) Resolve()
  • func (s Promise) Wait()
  • func (s Promise) WaitWithPeriodicTask(period time.Duration, task func())

Examples

• Promise.Wait
• Promise.WaitWithPeriodicTask

Types

type Promise

type Promise chan struct{}

Promise is a simple notification primitive for asynchronous events.

func (Promise) Resolve

func (s Promise) Resolve()

Resolve wakes any clients currently waiting on the Promise

func (Promise) Wait

func (s Promise) Wait()

Wait synchronously blocks until the Promise is resolved.

Example

var p = make(Promise)

go func() {
	// Do async work.
	time.Sleep(10 * time.Millisecond)
	fmt.Println("Async routine completes.")
	p.Resolve()
}()

fmt.Println("Pre-wait logic runs.")
p.Wait()
fmt.Println("Post-wait logic runs.")

Output:

Pre-wait logic runs.
Async routine completes.
Post-wait logic runs.

func (Promise) WaitWithPeriodicTask

func (s Promise) WaitWithPeriodicTask(period time.Duration, task func())

WaitWithPeriodicTask repeatedly invokes |task| with period |period| until the Promise is resolved.

Example

Unfortunately, this example is not made testable because it inherently operates as a race condition between two independent things. To get a deterministic test, the `resolve` would need to be triggered by the periodic task, making for an extremely contrived example. This example errs on the side of providing a more standard use case.

var p = make(Promise)

go func() {
	// Do async work.
	time.Sleep(50 * time.Millisecond)
	p.Resolve()
}()

var i int
p.WaitWithPeriodicTask(11*time.Millisecond, func() {
	i += 1
	fmt.Printf("%d\n", i)
})