hunk.code_window: 	}
   }
   func writeFileResponse(filename string, contentType string, contentSize int64, webserverMode string, fileReader io.Reader, forceDownload bool, w http.ResponseWriter, r *http.Request) *model.AppError {
   	w.Header().Set("Cache-Control", "private, no-cache")
   	w.Header().Set("X-Content-Type-Options", "nosniff")
   	if contentSize > 0 {
  
hunk.labels: keep keep keep replace keep keep keep keep
hunk.after_edit: func writeFileResponse(filename string, contentType string, contentSize int64, lastModification time.Time, webserverMode string, fileReader io.ReadSeeker, forceDownload bool, w http.ResponseWriter, r *http.Request) *model.AppError {
  
hunk.file_path: api4/file.go
hunk.type: replace
file: // Copyright 2013 The Go Authors.  All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // Adapted for dns package usage by Miek Gieben.
  
  package dns
  
  import "sync"
  import "time"
  
  // call is an in-flight or completed singleflight.Do call
  type call struct {
  	wg   sync.WaitGroup
  	val  *Msg
  	rtt  time.Duration
  	err  error
  	dups int
  }
  
  // singleflight represents a class of work and forms a namespace in
  // which units of work can be executed with duplicate suppression.
  type singleflight struct {
  	sync.Mutex                  // protects m
  	m          map[string]*call // lazily initialized
  
  	dontDeleteForTesting bool // this is only to be used by TestConcurrentExchanges
  }
  
  // Do executes and returns the results of the given function, making
  // sure that only one execution is in-flight for a given key at a
  // time. If a duplicate comes in, the duplicate caller waits for the
  // original to complete and receives the same results.
  // The return value shared indicates whether v was given to multiple callers.
  func (g *singleflight) Do(key string, fn func() (*Msg, time.Duration, error)) (v *Msg, rtt time.Duration, err error, shared bool) {
  	g.Lock()
  	if g.m == nil {
  		g.m = make(map[string]*call)
  	}
  	if c, ok := g.m[key]; ok {
  		c.dups++
  		g.Unlock()
  		c.wg.Wait()
  		return c.val, c.rtt, c.err, true
  	}
  	c := new(call)
  	c.wg.Add(1)
  	g.m[key] = c
  	g.Unlock()
  
  	c.val, c.rtt, c.err = fn()
  	c.wg.Done()
  
  	if !g.dontDeleteForTesting {
  		g.Lock()
  		delete(g.m, key)
  		g.Unlock()
  	}
  
  	return c.val, c.rtt, c.err, c.dups > 0
  }
  