Design Pattern: Chain Of Responsibility

consolelogger.go

type ConsoleLogger struct {
	next Logger
}

func (l *ConsoleLogger) Log(level LogLevel, text string) {
	fmt.Printf("%s | %s\n", level, text)
	if l.next != nil {
		l.next.Log(level, text)
	}
}

consolelogger_test.go

func TestConsoleLogger(t *testing.T) {
  logger := &ConsoleLogger{}
	expect := "haha"

  logger.Log(Info, expect)

	// check console output
}

emailogger.go

type EmailLogger struct {
	next Logger
}

func (l *EmailLogger) Log(level LogLevel, text string) {
	if level == Error {
		fmt.Printf("%s | sent alert email to me", level)
	}
	if l.next != nil {
		l.next.Log(level, text)
	}
}

logger.go

type LogLevel string

const (
	Info  LogLevel = "info"
	Error LogLevel = "error"
)

type Logger interface {
	Log(level LogLevel, text string)
}

func NewLogger() Logger {
	return &EmailLogger{
		next: &ConsoleLogger{},
	}
}

main.go

logger := NewLogger()
logger.Log(Info, "hello world")
logger.Log(Error, "the world has already ended due to zombies!")

// Output:
// info | hello world
// error | sent alert email to [email protected]
// error | the world has already ended due to zombies!

main_test.go

func TestLoggerChain(t *testing.T) {
	logger := NewLogger()
	expect := "haha"

	logger.Log(Error, expect)

	// check console output
	// check email is sent
}