arriqaaq

type FileSystem interface {
    Open() (io.ReadCloser, error)
    List() ([]string, error)
}

type File struct {
    name string
    path string
}

arriqaaq

type Logger interface {
    Println(v ...interface{})
    Fatalln(v ...interface{})
}

type Logrus struct {
    *logrus.Logger
}

func (l *Logrus) Println(v ...interface{}) {

arriqaaq

type Database interface {
    Insert(data interface{}) error
    Retrieve(id string) (interface{}, error)
}

type MySQL struct {
    connection *sql.DB
}

func (m *MySQL) Insert(data interface{}) error {

arriqaaq

package main

import (
    "fmt"
    "sync"
)

type LegacyService struct {
}

arriqaaq

package main

import "fmt"

type LegacyPrinter struct {
}

func (l *LegacyPrinter) Print(s string) {
    fmt.Println(s)
}

arriqaaq

type Database interface {
    SaveData(data string) error
}

type MySQL struct {
    // fields and methods
}

func (m *MySQL) SaveData(data string) error {
    // code to save data to MySQL

arriqaaq

type Singleton struct {
    count int
}

var instance *Singleton

func GetInstance() *Singleton {
    if instance == nil {
        instance = &Singleton{}
    }

arriqaaq

type Config struct {
    // fields and methods
}

var config *Config

func GetConfig() *Config {
    if config == nil {
        config = &Config{}
    }

arriqaaq

type Database struct {
    // fields and methods
}

var db *Database

func GetDatabase() *Database {
    if db == nil {
        db = &Database{}
    }

arriqaaq

type Logger struct {
    file *os.File
}

func (l *Logger) Log(message string) {
    _, _ = l.file.WriteString(message + "\n")
}

var logger *Logger