file/find.go
func Contain(filename string, b []byte) (bool, error) {
	f, err := os.Open(filename)
	if err != nil {
		return false, fmt.Errorf("Contain: %s", err)
	}
	defer f.Close()

	buf := bufio.NewReader(f)

	for {
		line, err := buf.ReadBytes('\n')
		if err == io.EOF {
			break
		}
		if bytes.Contains(line, b) {
			return true, nil
		}
	}
	return false, nil
}
func Contain(filename string, b []byte) (bool, error) {
	f, err := os.Open(filename)
	if err != nil {
		return false, fmt.Errorf("Contain: %s", err)
	}
	defer f.Close()

	buf := bufio.NewReader(f)

	for {
		line, err := buf.ReadBytes('\n')
		if err == io.EOF {
			break
		}
		if bytes.Contains(line, b) {
			return true, nil
		}
	}
	return false, nil
}
// Contain returns whether the named file contains the byte slice b. The
// return value is a boolean.