http - httputil DumpRequest Host header excluded?

Question

I am writing a http proxy which needs to call DumpRequest. For some reason, the client does not offer "Host" header while the server needs it. I then do this:

if req.Header.Get("host") == "" {
    req.Header.Set("Host", "www.domain.com:80")
}
data, _ := httputil.DumpRequest(req, true)
conn.Write(data)

The problem is after I set "host", data still does not has it. I digged into source code of DumpRequest, found this:

var reqWriteExcludeHeaderDump = map[string]bool{
    "Host":              true, // not in Header map anyway
    "Transfer-Encoding": true,
    "Trailer":           true,
}

Why is Host "not in Header map anyway"?

question from:https://stackoverflow.com/questions/65911820/httputil-dumprequest-host-header-excluded

Answer 1

Short answer

I guess you should use Header.Add() instead of Header.Set()

I didn't try it. So if my answer is wrong, be free to figure it out.

Reference

From source code , It said that.

It replaces any existing values associated with key

But in you case, you don't have that K existing. So it behaves as we expected.

If you use Set() method, it's cool.