确保传递到log.SetOutput的文件正确关闭

Consider this package that configures a logging adapter based on the environment, and allows changes to logging output at runtime.

package mylog

import (
    "log"
    "os"
    "io"
)

const StdOut = "STDOUT"

var logger *log.Logger

func init() {
    outputLocation := os.Getenv("MY_LOG_OUTPUT")
    if outputLocation == "" || outputLocation == StdOut {
        log.SetOutput(os.Stdout)
        return
    }

    f, _ := getFile(outputLocation)
    log.SetOutput(f)
}

func getFile(path string) (*os.File, error) {
    openFlags := os.O_WRONLY | os.O_APPEND | os.O_CREATE
    f, err := os.OpenFile(path, openFlags, 0666)
    if err != nil {
        return nil, err
    }

    return f, nil
}

func SetOutput(w io.Writer) {
    logger.SetOutput(w)
}

func Debug(v ...interface{}) {
    log.Println(v...)
}

There are two problems that I have with this:

1. There is not a way of being sure that w passed to SetOutput is a Closer.
2. Even if I could be sure (reflection?), when do I close it?

Edit: It's difficult to give a simple example of use case that causes a problem. For example, it I import this package into a simple program that runs and exits, I could expose a method to close log files and call that (with defer or without) before that program finishes execution. The real problem is with a long-running process (like a webserver) that does not have a point that you would want to close the log unless the process dies.

So part of my question is, is it even necessary to close the file?