code: func (p *Package) OpenSourceFile(name string) (*SourceFile, error) {
  	f := &SourceFile{Name: name, Package: p}
  	file, err := os.OpenFile(f.Abs(), os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
  	if err != nil {
  		return nil, err
  	}
  	f.osFile = file
  	return f, nil
  }
docs: // OpenSourceFile opens an existing file to append to it. If the file does not
  // exist OpenSourceFile creates it.