promise/future异步编程模型

原文： http://labs.strava.com/blog/futures-in-golang/

promise/future是一个非常重要的异步编程模型，它可以让我们摆脱传统的回调陷阱，从而使用更加优雅、清晰的方式进行异步编程

package main

import (
    "net/http"
    "io/ioutil"
    "fmt"
)

func main() {
    url := "http://www.google.com"
    future := Future(func() (interface{}, error) {
        resp, err := http.Get(url)
        if err != nil {
            return nil, err
        }
        defer resp.Body.Close()
        return ioutil.ReadAll(resp.Body)

    })

    // do many other things
    b, err := future()
    body, _ := b.([]byte)
    fmt.Printf("response length: %d", len(body))
    fmt.Printf("request error: %v", err)
}
func Future(f func() (interface{}, error)) func() (interface{}, error) {
    var result interface{}
    var err error

    c := make(chan struct{}, 1)
    go func() {
        defer close(c)
        result, err = f()
    }()

    return func() (interface{}, error) {
        <-c
        return result, err
    }
}