匿名函数似乎未在Go例程中执行

Question

I have the following code. Pay special attention to the anonymous function:

func saveMatterNodes(matterId int, nodes []doculaw.LitigationNode) (bool, error) {

    var (
        err  error
        resp *http.Response
    )

    // Do this in multiple threads
    for _, node := range nodes {
        fmt.Println("in loops")
        go func() {
            postValues := doculaw.LitigationNode{
                Name:        node.Name,
                Description: node.Description,
                Days:        node.Days,
                Date:        node.Date,
                IsFinalStep: false,
                Completed:   false,
                Matter:      matterId}

            b := new(bytes.Buffer)
            json.NewEncoder(b).Encode(postValues)
            resp, err = http.Post("http://127.0.0.1:8001/matterNode/", "application/json", b)
            io.Copy(os.Stdout, resp.Body)

            fmt.Println("Respone from http post", resp)
            if err != nil {
                fmt.Println(err)
            }
        }()

    }

    if err != nil {
        return false, err
    } else {
        return true, nil
    }

}

If I remove the go func() {}() part and just leave the code in between it seems to execute fine but the moment I add it back it does not execute. Any idea why that is? I initially thought maybe because it's executing on a different thread but this doesn't seem to be the case as I can see on my webservice access logs that it is not executing.

Answer 1

I think this behaviour is because function never yields back to main thread ( After you launch goroutines, there is no construct in program to wait for them to finish their work). Use of channels, IO operations, sync.WaitGroup etc can yield control back to the main thread.

You may want to try sync.WaitGroup

Example: https://play.golang.org/p/Zwn0YBynl2