Modeled after Golang's ioutil package's NopCloser method which wraps an io.Reader interface in an io.ReadCloser facade interface, this code takes an io.Writer and a nil channel and returns an io.WriteCloser interface. The example.go file demonstrates usage in an http.HandleFunc as a very over complicated counter using the worker-and-channel-over…

example.go

package main

import (
	"io"
	"log"
	"net/http"
	"strconv"
)

func main() {
	worker := NewWorker()
	http.HandleFunc("/count", func(w http.ResponseWriter, r *http.Request) {
		doneChan := make(chan struct{})
		worker.request <- WriteChanCloser(w, doneChan)
		<-doneChan
	})
	err := http.ListenAndServe(":8888", nil)
	if err != nil {
		log.Fatal("ListenAndServe: ", err)
	}
}

type Worker struct {
	count   int
	request chan io.WriteCloser
}

func (w *Worker) run() {
	go func() {
		for {
			select {
			case req := <-w.request:
				w.count += 1
				req.Write([]byte(strconv.Itoa(w.count)))
				req.Close()
			}
		}
	}()
}

func NewWorker() *Worker {
	w := &Worker{
		count:   0,
		request: make(chan io.WriteCloser),
	}
	w.run()
	return w
}

WriteChanCloser.go

package main

import "io"

type writeChanCloser struct {
	io.Writer
	closeChan chan struct{}
}

func (wcc writeChanCloser) Close() error {
	close(wcc.closeChan)
	return nil
}

// WriteChanCloser returns a WriteCloser with a Close method wrapping
// the provided Reader r.  The Close method simply closes the provided
// nil channel.
func WriteChanCloser(r io.Writer, c chan struct{}) io.WriteCloser {
	return writeChanCloser{r, c}
}