async

A ES7-style async/await implementation lib based on Goroutine + Channel in Golang.

Install

$ go get github.com/sun0day/async

API

async.AsyncTask

Async work unit created by async.Async.

type AsyncTask[V any] struct {
  Value   V  // execution result
  Err     any // execution possible error
  State   AsyncState // execution state
}

async.AsyncTask.State has 3 values:

• async.PENDING(async.AsyncTask is doing)
• async.FULFILLED(async.AsyncTask is done and result returns)
• async.REJECTED(async.AsyncTask is done but error happens).

async.Async

Convert a synchronous func to be asynchronous.

Type definition

func Async[V any](f func() V) func() *AsyncTask[V] {...}

Usage

package main

import (
  "fmt"
  "time"
  "github.com/sun0day/async"
)

func main() {
  a := 1
  b := 2
  f := func() int {
    c := a + b
    fmt.Printf("async result=%d\n", c)
    return c
  }

  af := async.Async[int](f)

  fmt.Printf("sync start, goroutine=%d\n", runtime.NumGoroutine())
  af()
  fmt.Printf("sync end, goroutine=%d\n", runtime.NumGoroutine())
  time.Sleep(1 * time.Second)
  fmt.Printf("async end, goroutine=%d\n", runtime.NumGoroutine())
}

/* stdout
sync start, goroutine=1
sync end, goroutine=2
async result=3
async end, goroutine=1
*/

async.Await

Wait async.AsyncTask to be done.

Type definition

func Await[V any](t *AsyncTask[V]) (V, any) {...}

Usage

package main

import (
  "fmt"
  "runtime"
  "github.com/sun0day/async"
)

func main() {
  a := 1
  b := 2
  f1 := func() int {
    c := a + b
    return c
  }

  f2 := func() int {
    panic("f() error")
  }

  af1 := async.Async[int](f1)
  af2 := async.Async[int](f2)

  fmt.Printf("sync start, goroutine=%d\n", runtime.NumGoroutine())
  value, _ := async.Await[int](af1())
  _, err := async.Await[int](af2())
  fmt.Printf("af1 result=%d\n", value)
  fmt.Printf("af2 error=%s\n", err)
  fmt.Printf("sync end, goroutine=%d\n", runtime.NumGoroutine())
}
/* stdout
sync start, goroutine=1
af1 result=3
af2 error=f() error
sync end, goroutine=1
*/

async.All

Asynchronously return values(when all funcs are finished) or error(once one of funcs throws error).

Type definition

func All[V any](fs []func() V) *AsyncTask[[]V] {...}

Usage

package main

import (
  "fmt"
  "runtime"
  "time"
  "github.com/sun0day/async"
)

func main() {
  a := 1
  b := 2
  f1 := func() int {
    time.Sleep(1 * time.Second)
    c := a + b
    return c
  }

  f2 := func() int {
    time.Sleep(2 * time.Second)
    c := a * b
    return c
  }

  f3 := func() int {
    panic("f3 error")
  }

  fmt.Printf("sync start, goroutine=%d\n", runtime.NumGoroutine())
  values, _ := async.Await[[]int](async.All[int]([]func() int{f1, f2}))
  _, err := async.Await[[]int](async.All[int]([]func() int{f1, f2, f3}))
  fmt.Printf("all result=%v\n", values)
  fmt.Printf("all error=%s\n", err)
  fmt.Printf("sync end, goroutine=%d\n", runtime.NumGoroutine())
}
/* stdout
sync start, goroutine=1
all result=[3 2]
all error=f3 error
sync end, goroutine=1
*/

async.Race

Asynchronously return value or error of the fisrt finished func.

Type definition

func Race[V any](fs []func() V) *AsyncTask[V] {...}

Usage

package main

import (
  "fmt"
  "runtime"
  "time"
  "github.com/sun0day/async"
)

func main() {
  a := 1
  b := 2
  f1 := func() int {
    time.Sleep(1 * time.Second)
    c := a + b
    return c
  }

  f2 := func() int {
    time.Sleep(2 * time.Second)
    c := a * b
    return c
  }

  fmt.Printf("sync start, goroutine=%d\n", runtime.NumGoroutine())
  value, _ := async.Await[int](async.Race[int]([]func() int{f1, f2}))
  fmt.Printf("race result=%d\n", value)
  fmt.Printf("sync end, goroutine=%d\n", runtime.NumGoroutine())
}
/* stdout
sync start, goroutine=1
race result=3
sync end, goroutine=2
*/