Using Span produces an exception in VS 2019

Question

I have added the reference System.Memory to a Console C# project in VS 2019 to use System.Span structure. But the following code produces an exception:

using System;
class A
{
    static void Main()
    {
        Span<int> numbers = stackalloc int[3];            
    }
}

The exception message is:

Inner Exception FileNotFoundException: Could not load file or assembly 'System.Runtime.CompilerServices.Unsafe, Version=4.0.4.1, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.

How can I solve the problem and remove the exception?