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: compress.go
    path of file: ./repos/go-starter-kit/vendor/github.com/labstack/echo/middleware
    
    the code of the file until where you have to start completion: package middleware

import (
	"bufio"
	"compress/gzip"
	"io"
	"io/ioutil"
	"net"
	"net/http"
	"strings"

	"github.com/labstack/echo"
)

type (
	// GzipConfig defines the config for Gzip middleware.
	GzipConfig struct {
		// Skipper defines a function to skip middleware.
		Skipper Skipper

		// Gzip compression level.
		// Optional. Default value -1.
		Lev
    
func GzipWithConfig(config GzipConfig) echo.MiddlewareFunc {
	// Defaults
	if config.Skipper == nil {
		config.Skipper = DefaultGzipConfig.Skipper
	}
	if config.Level == 0 {
		config.Level = DefaultGzipConfig.Level
	}

	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			if config.Skipper(c) {
				return next(c)
			}

			res := c.Response()
			res.Header().Add(echo.HeaderVary, echo.HeaderAcceptEncoding)
			if strings.Contains(c.Request().Header.Get(echo.HeaderAcceptEncoding), gzipScheme) {
				rw := res.Writer
				w, err := gzip.NewWriterLevel(rw, config.Level)
				if err != nil {
					return err
				}
				defer func() {

					if res.Size == 0 {
						// We have to reset response to it's pristine state when
						// nothing is written to body or error is returned.
						// See issue #424, #407.
						res.Writer = rw
						w.Reset(ioutil.Discard)
					}
					w.Close()
				}()
				grw := &gzipResponseWriter{Writer: w, ResponseWriter: rw}
				res.Writer = grw
			}
			return next(c)
		}
	}
}