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: multiwriter.go
    path of file: ./repos/devspace/vendor/github.com/moby/buildkit/util/progress/progresswriter
    
    the code of the file until where you have to start completion: package progresswriter

import (
	"context"
	"strings"
	"sync"

	"github.com/moby/buildkit/client"
	"golang.org/x/sync/errgroup"
)

type MultiWriter struct {
	w     Writer
	eg    *errgroup.Group
	once  sync.Once
	ready chan struct{}
}

func (mw *MultiWriter) WithPrefix(pfx string, force
    
func (mw *MultiWriter) WithPrefix(pfx string, force bool) Writer {
	in := make(chan *client.SolveStatus)
	out := mw.w.Status()
	p := &prefixed{
		main: mw.w,
		in:   in,
	}
	mw.eg.Go(func() error {
		mw.once.Do(func() {
			close(mw.ready)
		})
		for {
			select {
			case v, ok := <-in:
				if ok {
					if force {
						for _, v := range v.Vertexes {
							v.Name = addPrefix(pfx, v.Name)
						}
					}
					out <- v
				} else {
					return nil
				}
			case <-mw.Done():
				return mw.Err()
			}
		}
	})
	return p
}