golang request redirection problem (redundant error)

When using golang to make network requests, you may occasionally encounter request redirection problems. This problem may be caused by redundant errors. PHP editor Xigua will tell you how to solve this problem to ensure the smooth progress of network requests. Let’s take a look!

Question content

I'm getting a very strange behavior from golang.

I want to do something with a post request and then redirect the request. Depends on random factors...whether it works or not.

When it doesn't work, I get this error:

"http: redundant response. WriteHeader call from..."

The deeper the function, the less likely the redirection will work.

• As far as I know, I only redirected once (or zero times...)
• I don't write the header before redirecting.
• The only thing I did to the writer before redirecting was put it into a map.

I don't want to copy all the code here, so I'll summarize it.

The handler handles POST requests, passing the request data in a map named demand.

Then parse the request to get the form value and save it into demand It is sent to the channel.

The demand graph is passed from the channel to the following function:

func answer_login(demand map[string]any) map[string]any {
    writer := demand["writer"].(http.ResponseWriter)
    request := demand["request"].(*http.Request)
    http.Redirect(writer, request, "/", 302) // <- if it is here it works (at95 %)
    // some mundane code (printing stuff, really)
    .
    .
    .
    // http.Redirect(writer, request, "/", 302) // <- if it is here it works (only at 20 %)
    ...

If I press F5, it eventually redirects correctly. I tried simply writing something in writer.Write([]byte("same issues")), same issue.

I'm on Linux and have tried different browsers.

Question: Is this a (known) bug?

Is there any solution?

(Force writing to client)

Thank you

Solution

I finally understood the problem and found a solution.
question:

Therefore, writer requests are processed and redirected in a different scope function than the actual processing function. and when the actualhandling function ends. Certain contextual factors cause a writer request to expire: you can no longer redirect or respond to the request. This is what is written in the documentation:

https://pkg.go.dev/net/http p>

One possible explanation for why it works sometimes is... maybe the "channel transfer, processing and redirection" happens fast enough (sometimes) and the actual handler function hasn't been closed yet .

Blocking handler functions before processing data defeats the purpose of parallel asynchronous processing. So I ended up nesting everything inside a handler function.
Smart people are welcome to correct me or share better explanations about context and ResponseWriters.

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