main.go

package golangglobalcachewithmutex

import "sync"

type MemCache[K comparable, T any] struct {
	cache map[K]T
	mutex *sync.Mutex
}

func (m MemCache[K, T]) Get(key K) (T, bool) {
	m.mutex.Lock()
	defer m.mutex.Unlock()
	value, ok := m.cache[key]
	return value, ok
}

func (m MemCache[K, T]) Set(key K, value T) {
	m.mutex.Lock()
	defer m.mutex.Unlock()
	m.cache[key] = value
}

func (m MemCache[K, T]) Delete(key K) {
	m.mutex.Lock()
	defer m.mutex.Unlock()
	delete(m.cache, key)
}

func NewMemCache[K comparable, T any]() MemCache[K, T] {
	return MemCache[K, T]{
		cache: make(map[K]T),
		mutex: &sync.Mutex{},
	}
}

main_test.go

package golangglobalcachewithmutex

import "testing"

func Test_Get(t *testing.T) {
	cache := NewMemCache[string, int]()
	cache.Set("foo", 1)
	value, ok := cache.Get("foo")
	if !ok {
		panic("value should exist")
	}
	if value != 1 {
		panic("value should be 1")
	}
}

func Test_Get_WhenKeyDoesNotExist(t *testing.T) {
	cache := NewMemCache[string, int]()
	_, ok := cache.Get("foo")
	if ok {
		panic("value should not exist")
	}
}

func Test_Set(t *testing.T) {
	cache := NewMemCache[string, int]()
	cache.Set("foo", 1)
	value, ok := cache.Get("foo")
	if !ok {
		panic("value should exist")
	}
	if value != 1 {
		panic("value should be 1")
	}
}

func Test_Delete(t *testing.T) {
	cache := NewMemCache[string, int]()
	cache.Set("foo", 1)
	cache.Delete("foo")
	_, ok := cache.Get("foo")
	if ok {
		panic("value should not exist")
	}
}