Added Singleton

Misc/Initialization.go

@@ -0,0 +1,28 @@
+package Misc
+
+import "sync"
+
+type Singleton[T any] struct {
+	once sync.Once
+	Val  Nullable[T]
+	Init func() Result[T]
+}
+
+func NewSingleton[T any](f func() Result[T]) *Singleton[T] {
+	return &Singleton[T]{
+		Init: f,
+		Val:  NewNullable[T](),
+	}
+}
+
+func (this *Singleton[T]) Get() Result[T] {
+	var err error
+	this.once.Do(func() {
+		if this.Val.IsNil {
+			newObj := this.Init()
+			this.Val.Value = newObj.Value
+			err = newObj.Err
+		}
+	})
+	return Result[T]{Value: this.Val.Value, Err: err}
+}

Tests/Misc/Initialization_test.go

@@ -0,0 +1,19 @@
+package Misc
+
+import (
+	"github.com/RENCI/GoUtils/Misc"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func Test_Singleton(t *testing.T) {
+
+	r := 1
+	s := Misc.NewSingleton(func() Misc.Result[int] {
+		r += 1
+		return Misc.NewResult(r, nil)
+	})
+	res := s.Get()
+	res = s.Get()
+	assert.Equal(t, 2, res.Value)
+}