使用 GO 获取方向时如何使用 Context？

Question

我正在使用以下代码从 Google 云端获取方向：

import (
    "google.golang.org/appengine"
    "google.golang.org/appengine/urlfetch"
    "fmt"
    "io/ioutil"
    "net/http"
)

const directionAPIKey = "APIKey"
const directionURL = "https://maps.googleapis.com/maps/api/directions/json?origin=%s&destination=%s&mode=%s&key=%s"

func main() {
    http.HandleFunc("/", handler)
}

func handler(w http.ResponseWriter, r *http.Request) {
    ctx := appengine.NewContext(r)
    direction, err := fetchDirection(ctx, r.FormValue("origin"), r.FormValue("destination"), r.FormValue("mode"))
    if err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }
    w.Header().Add("Content-Type", "application/json; charset=utf-8")
    w.Write(direction)
}

func fetchDirection(ctx appengine.Context, origin string, destination string, mode string) ([]byte, error) {
    client := urlfetch.Client(ctx)
    resp, err := client.Get(fmt.Sprintf(directionURL, origin, destination, mode, directionAPIKey))
    if err != nil {
        return nil, err
    }
    defer resp.Body.Close()
    return ioutil.ReadAll(resp.Body)
}

但是我得到一个错误：

undefined: appengine.Context

尝试部署应用程序时。我尝试过的是改变：

ctx := appengine.NewContext(r)

进入

ctx := r.Context()

和

func fetchDirection(ctx appengine.Context, origin string...)

进入

func fetchDirection(ctx Context, origin string...)

但我得到：

undefined: Context

我完全迷路了。我是 Go 和 GCP 的新手，所以请耐心等待。谢谢

Answer 1

如果勾选 godoc for urlfetch you'll see it links to where the Context type is defined. That in turn tells you that "As of Go 1.7 this package is available in the standard library under the name context. https://golang.org/pkg/context."

所以添加一个导入：

import "context"

并将其称为：

func fetchDirection(ctx context.Context, origin string...)

使用 GO 获取方向时如何使用 Context？

How to use Context when getting a direction with GO?

go

google-cloud-platform

google-app-engine-golang