Golang 帮看一下，运行的时候 panic，原因是写入了关闭的 channel，请问该如何解决？

netboy · 2019-09-19 13:23:16 · 1271 次点击

package main

import (
    "context"
    "errors"
    "fmt"
    "sync"
    "time"
)

type Detail struct {
    ID string
}

func Get(ctx context.Context, id string) (*Detail, error) {
    //you can call this function directly
    time.Sleep(time.Second * 3)
    if id == "3" {
        return nil, errors.New("error id is 3")
    }
    return &Detail{ID: id}, nil
}

func GetAll(ctx context.Context, ids []string) (map[string]*Detail, error) {
    var swg sync.WaitGroup
    result := make(map[string]*Detail, len(ids))
    detailChan := make(chan *Detail, 3)
    doneChan := make(chan struct{}, 1)
    errChan := make(chan error, 1)
    defer close(detailChan)
    defer close(doneChan)
    defer close(errChan)

    ctx, cancel := context.WithCancel(ctx)

    for _, value := range ids {
        swg.Add(1)
        go func(ctx context.Context, v string) {
            defer swg.Done()
            res, err := Get(ctx, v)
            if err != nil {
                fmt.Println("get error ", err, v)
                errChan <- err
                return
            }
            detailChan <- res
            /*
                select {
                case <-ctx.Done():
                    return
                default:
                    detailChan <- res
                }
            */
        }(ctx, value)
    }

    go func() {
        for value := range detailChan {
            fmt.Println("range ", value)
            result[value.ID] = value
        }
    }()

    go func() {
        swg.Wait()
        doneChan <- struct{}{}
    }()

    select {
    case err := <-errChan:
        fmt.Println("select error:", err)
        cancel()
        return nil, err
    case <-doneChan:
        fmt.Println("select done")
    }
    return result, nil
}

func main() {
    str := []string{"1", "2", "3", "4", "5", "6"}
    GetAll(context.Background(), str)
    fmt.Println("end")
}