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: cacheOnReadFs.go
    path of file: ./repos/minicron/client/vendor/github.com/spf13/afero
    
    the code of the file until where you have to start completion: package afero

import (
	"os"
	"syscall"
	"time"
)

// If the cache duration is 0, cache t
    
func (u *CacheOnReadFs) OpenFile(name string, flag int, perm os.FileMode) (File, error) {
	st, _, err := u.cacheStatus(name)
	if err != nil {
		return nil, err
	}
	switch st {
	case cacheLocal, cacheHit:
	default:
		if err := u.copyToLayer(name); err != nil {
			return nil, err
		}
	}
	if flag&(os.O_WRONLY|syscall.O_RDWR|os.O_APPEND|os.O_CREATE|os.O_TRUNC) != 0 {
		bfi, err := u.base.OpenFile(name, flag, perm)
		if err != nil {
			return nil, err
		}
		lfi, err := u.layer.OpenFile(name, flag, perm)
		if err != nil {
			bfi.Close() // oops, what if O_TRUNC was set and file opening in the layer failed...?
			return nil, err
		}
		return &UnionFile{base: bfi, layer: lfi}, nil
	}
	return u.layer.OpenFile(name, flag, perm)
}