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: purge.go
    path of file: ./repos/etcd/client/pkg/fileutil
    
    the code of the file until where you have to start completion: // Copyright 2015 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package fi
    
func purgeFile(lg *zap.Logger, dirname string, suffix string, max uint, interval time.Duration, stop <-chan struct{}, purgec chan<- string, donec chan<- struct{}, flock bool) <-chan error {
	if lg == nil {
		lg = zap.NewNop()
	}
	errC := make(chan error, 1)
	lg.Info("started to purge file",
		zap.String("dir", dirname),
		zap.String("suffix", suffix),
		zap.Uint("max", max),
		zap.Duration("interval", interval))

	go func() {
		if donec != nil {
			defer close(donec)
		}
		for {
			fnames, err := ReadDir(dirname)
			if err != nil {
				errC <- err
				return
			}
			newfnames := make([]string, 0)
			for _, fname := range fnames {
				if strings.HasSuffix(fname, suffix) {
					newfnames = append(newfnames, fname)
				}
			}
			sort.Strings(newfnames)
			fnames = newfnames
			for len(newfnames) > int(max) {
				f := filepath.Join(dirname, newfnames[0])
				var l *LockedFile
				if flock {
					l, err = TryLockFile(f, os.O_WRONLY, PrivateFileMode)
					if err != nil {
						lg.Warn("failed to lock file", zap.String("path", f), zap.Error(err))
						break
					}
				}
				if err = os.Remove(f); err != nil {
					lg.Error("failed to remove file", zap.String("path", f), zap.Error(err))
					errC <- err
					return
				}
				if flock {
					if err = l.Close(); err != nil {
						lg.Error("failed to unlock/close", zap.String("path", l.Name()), zap.Error(err))
						errC <- err
						return
					}
				}
				lg.Info("purged", zap.String("path", f))
				newfnames = newfnames[1:]
			}
			if purgec != nil {
				for i := 0; i < len(fnames)-len(newfnames); i++ {
					purgec <- fnames[i]
				}
			}
			select {
			case <-time.After(interval):
			case <-stop:
				return
			}
		}
	}()
	return errC
}