You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: gzip.go
    path of file: ./repos/kubernetes/vendor/github.com/NYTimes/gziphandler
    
    the code of the file until where you have to start completion: package gziphandler // import "github.com/NYTimes/gziphandler"

import (
	"bufio"
	"compress/gzip"
	"fmt"
	"io"
	"mime"
	"net"
	"net/http"
	"strconv"
	"strings"
	"sync"
)

const (
	vary            = "Vary"
	acceptEncoding  = "Accept-Encoding"
	contentEncoding = "Content-Encoding"
	contentType     = "Content-Type"
	contentLength   = "Content-Length"
)

type codings map[string]float64

const (
	// DefaultQValue is the default qvalue to assign to an encoding if no explicit qvalue is set.
	// This is actually kind of ambiguous in RFC 2616, so hopefully it's correct.
	// The examples seem to indicate that it is.
	DefaultQValue = 1.0

	// DefaultMinSize is the default minimum size until we enable gzip compression.
	// 1
    
func (w *GzipResponseWriter) startGzip() error {
	// Set the GZIP header.
	w.Header().Set(contentEncoding, "gzip")

	// if the Content-Length is already set, then calls to Write on gzip
	// will fail to set the Content-Length header since its already set
	// See: https://github.com/golang/go/issues/14975.
	w.Header().Del(contentLength)

	// Write the header to gzip response.
	if w.code != 0 {
		w.ResponseWriter.WriteHeader(w.code)
		// Ensure that no other WriteHeader's happen
		w.code = 0
	}

	// Initialize and flush the buffer into the gzip response if there are any bytes.
	// If there aren't any, we shouldn't initialize it yet because on Close it will
	// write the gzip header even if nothing was ever written.
	if len(w.buf) > 0 {
		// Initialize the GZIP response.
		w.init()
		n, err := w.gw.Write(w.buf)

		// This should never happen (per io.Writer docs), but if the write didn't
		// accept the entire buffer but returned no specific error, we have no clue
		// what's going on, so abort just to be safe.
		if err == nil && n < len(w.buf) {
			err = io.ErrShortWrite
		}
		return err
	}
	return nil
}