package main

import (
    "compress/gzip"
    "net/http"
    "strings"
)

const Level int = -1

func myHandler(w http.ResponseWriter, r *http.Request) {
    if strings.Contains(r.Header.Get("TE"), "gzip") {
        writer, err := gzip.NewWriterLevel(w, Level)
        if err != nil {
            panic(err)
        }
        w.Header().Set("Transfer-Encoding", "gzip")
        writer.Write([]byte("Some content..."))
    } else {
        w.Write([]byte("Couldn't gzip (not accepted)"))
    }
}

func main() {
    http.ListenAndServe(":8080", http.HandlerFunc(myHandler))
}

        ...
        if hasTE && te == "identity" {
            cw.chunking = false
            w.closeAfterReply = true
        } else if hasTE && te == "chunked" {
            cw.chunking = true
            setHeader.transferEncoding = "chunked"
            delHeader("Transfer-Encoding")
        } else {
            // HTTP/1.1 or greater: use chunked transfer encoding
            ...