From e57918df0528eca1d3074bd189f246493ea7102e Mon Sep 17 00:00:00 2001
From: wangwenbin <wangwenbin@dodjoy.com>
Date: Thu, 28 Dec 2023 17:41:52 +0800
Subject: [PATCH] =?UTF-8?q?ErrGroup=E4=BD=BF=E7=94=A8=E5=9C=BA=E6=99=AF?=
 =?UTF-8?q?=E7=A4=BA=E4=BE=8B?=
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---
 err_group/weather.go      | 80 +++++++++++++++++++++++++++++++++++++++
 err_group/weather_test.go | 17 +++++++++
 2 files changed, 97 insertions(+)
 create mode 100644 err_group/weather.go
 create mode 100644 err_group/weather_test.go

diff --git a/err_group/weather.go b/err_group/weather.go
new file mode 100644
index 0000000..1ebe5d2
--- /dev/null
+++ b/err_group/weather.go
@@ -0,0 +1,80 @@
+package err_group
+
+import (
+	"context"
+	"golang.org/x/sync/errgroup"
+	"math/rand"
+	"time"
+)
+
+type WeatherData struct {
+	City    string
+	Weather string
+	Temp    int
+}
+
+var WeatherList = []string{"晴", "阴", "多云", "小雨", "大雨"}
+
+// fetchWeatherData 获取天气数据
+func fetchWeatherData(ctx context.Context, city string) (*WeatherData, error) {
+	done := make(chan struct{}, 1) // 用于指示数据获取成功完成
+	data := new(WeatherData)
+
+	// 启动一个goroutine来获取天气数据
+	go func() {
+		// 这里仅为示例，实际中这里会是API调用
+		// 为了模拟可能出现的超时或错误情况，这里随机地休眠一段时间
+		time.Sleep(time.Duration(rand.Intn(500)) * time.Millisecond)
+		data.City = city
+		// 随机天气
+		data.Weather = WeatherList[rand.Intn(len(WeatherList))]
+		// 随机温度
+		data.Temp = rand.Intn(40)
+		done <- struct{}{}
+	}()
+
+	select {
+	case <-ctx.Done():
+		// 如果上下文被取消，返回错误
+		return nil, ctx.Err()
+	case <-done:
+		// 如果数据获取成功完成，返回数据
+		return data, nil
+	}
+}
+
+func GetAllCityWeatherData(timeOut time.Duration) ([]*WeatherData, error) {
+	// 创建一个携带cancel的context
+	ctx, cancel := context.WithTimeout(context.Background(), timeOut)
+	defer cancel() // 确保所有路径都调用cancel
+	list := make([]*WeatherData, 0)
+
+	// 初始化一个ErrGroup对象
+	g, ctx := errgroup.WithContext(ctx)
+
+	// 城市列表
+	cities := []string{"New York", "Tokyo", "Berlin", "Paris", "Beijing"}
+
+	// 循环启动goroutine来获取每个城市的天气数据
+	for _, city := range cities {
+		city := city
+		g.Go(func() error {
+			// FetchWeatherData使用了上下文，如果上下文被取消，它应该立刻尝试返回
+			data, err := fetchWeatherData(ctx, city)
+			if err != nil {
+				return err
+			}
+
+			// 如果没有错误，将数据添加到列表中
+			list = append(list, data)
+			return nil
+		})
+	}
+
+	// 等待所有goroutine完成或出现错误
+	if err := g.Wait(); err != nil {
+		return nil, err
+	}
+
+	return list, nil
+}
diff --git a/err_group/weather_test.go b/err_group/weather_test.go
new file mode 100644
index 0000000..e1245c2
--- /dev/null
+++ b/err_group/weather_test.go
@@ -0,0 +1,17 @@
+package err_group
+
+import (
+	"testing"
+	"time"
+)
+
+func TestGetAllCityWeatherData(t *testing.T) {
+	list, err := GetAllCityWeatherData(500 * time.Millisecond)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, data := range list {
+		t.Logf("%s: %s, %d", data.City, data.Weather, data.Temp)
+	}
+}