Singleton for PowerShell class

ClassSingleton-DO.ps1

function Main() {
    $item = [Singleton]::Instance
    $item -eq $null #false

    $item.SingletonTarget # Singleton object GUID will return
    $item.SingletonTarget # Same object

    $item2 = [Singleton]::Instance # same instance
    $item -eq $item2 # true
}

# There is no documentation for static field "Thread-safeness" but if it is safe, then this Singleton guaranteed thread-safety.
# https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_classes?view=powershell-5.1#static-attribute

# Also PowerShell Class doesn't have readonly or getter only keyword to protect field to be overwrite after instantiate.
# Make sure user MUST NOT set [Singleton]::Instance field.
class Singleton {
    hidden static [Singleton] $_instance = [Singleton]::new()
    static [Singleton] $Instance = [Singleton]::GetInstance()

    [Guid] $SingletonTarget = [Guid]::NewGuid()

    hidden Singleton() {
    }

    hidden static [Singleton] GetInstance() {
        return [Singleton]::_instance
    }
}

ClassSingleton-DONT.ps1

function Main() {
    $item = [Singleton]::Instance
    $item -eq $null # true
    $item.SingletonTarget # $null
}

# PowerShell static field initialize as it's order, therefore this always return $null for "_instance"
class Singleton {
    static [Singleton] $Instance = [Singleton]::GetInstance()
    hidden static [Singleton] $_instance = [Singleton]::new()

    [Guid] $SingletonTarget = [Guid]::NewGuid()

    hidden Singleton() {
    }

    hidden static [Singleton] GetInstance() {
        return [Singleton]::_instance
    }
}

LazySingleton.cs

// Thread-safe and full lazy-ness singleton.
void Main()
{
    Singleton.Instance.target.Dump();
}

public class Singleton
{
    private static readonly Lazy<Singleton> lazy = new Lazy<Singleton>(() => new Singleton());
    
    public static Singleton Instance { get { return lazy.Value; } }

    private Singleton()
    {
    }
}

SimpleSingleton.cs

// Thread-safe Singleton, but much less lazyness for all properties/fields.
void Main()
{
    Singleton.Instance.target.Dump();
}

class Singleton
{
    public static Singleton Instance
    {
        get
        {
            return instance;
        }
    }
    private static Singleton instance = new Singleton();
    
    public Guid target = Guid.NewGuid();
}