Brotli compression not working

[mateors]

import brotli_enc "gopkg.in/kothar/brotli-go.v0/enc"

compressor := middleware.NewCompressor(5, "text/html")
compressor.SetEncoder("br", func(w http.ResponseWriter, level int) io.Writer {
  params := brotli_enc.NewBrotliParams()
  params.SetQuality(level)
  return brotli_enc.NewBrotliWriter(params, w)
})

the above code shows error, but following seems working but compression not working what's wrong?

	r := chi.NewRouter() //chi.NewMux()
	//r.Use(middleware.Logger)

	compressor := middleware.NewCompressor(5, "/*") //"/*"
	compressor.SetEncoder("br", func(w io.Writer, level int) io.Writer {
		params := brotli_enc.NewBrotliParams()
		params.SetQuality(level)
		return brotli_enc.NewBrotliWriter(params, w)
	})
	r.Use(compressor.Handler) //