func newFileWriter(fileName string) (writer *fileWriter, err error) {
	newWriter := new(fileWriter)
	newWriter.fileName = fileName
	return newWriter, nil
}
Creates a new file and a corresponding writer. Returns error, if the file couldn't be created.
package seelog
import (
	"fmt"
	"io"
	"os"
	"path/filepath"
)
type fileWriter struct {
	innerWriter io.WriteCloser
	fileName    string
}