BUG: lambdaurl.Wrap still does not add Content-Length headers?

[suntong]

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is.

Following #508,

The http.ResponseWriter implementation says the following thing about Content-Type header (and it actually has a note about Content-Length too).

If WriteHeader has not yet been called, Write calls
WriteHeader(http.StatusOK) before writing the data. If the Header
does not contain a Content-Type line, Write adds a Content-Type set
to the result of passing the initial 512 bytes of written data to
DetectContentType. Additionally, if the total size of all written
data is under a few KB and there are no Flush calls, the
Content-Length header is added automatically.

As of right now the lambdaurl.Wrap implementation completely misses this . . .

which get closed as a part of https://github.com/aws/aws-lambda-go/releases/tag/v1.42.0

However a quick search of Content-Length in the change log of
v1.41.0...v1.42.0

did not get any hits:

Are the Content-Length headers being added now?

Describe the solution you'd like

Add the Content-Length headers, properly.

Additional context

For a handler like:

				mux.HandleFunc("/hello", func(w http.ResponseWriter, r *http.Request) {
					w.WriteHeader(200)
					_, _ = w.Write([]byte("Hello World!"))
				})

I was able to get return from it if I try it locally, However, if using lambdaurl, I got empty returns, i.e., Content-Length: 0.

Please double-check. Thanks

[suntong]

Describe the solution you'd like

Add the Content-Length headers.

As the Content-Length header is not added by the lib. Ref:
https://github.com/search?q=repo%3Aaws%2Faws-lambda-go+Content-Length&type=code

However, It seems to be more than that for a proper fix, as I tried to add the Content-Length headers myself but it has no effect at all:

	mux.HandleFunc("/hello", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Length", "12") // len("Hello World!")
		w.WriteHeader(200)
		w.Write([]byte("Hello World!"))

	})