title: How do I reference System.Span<T> in my dotnet core project?
body: <p>Everybody seems to suggest that it's already available, but I cannot for the life of me figure out how to get <code>System.Span&lt;T&gt;</code>.</p>
  
  <p>The <a href="https://docs.microsoft.com/en-us/dotnet/api/system.span-1?view=netcore-2.0" rel="nofollow noreferrer">documentation says ".Net Core 2.0"</a>, and <a href="https://blogs.msdn.microsoft.com/dotnet/2017/11/15/welcome-to-c-7-2-and-span/" rel="nofollow noreferrer">this post from Mads Torgerson</a> suggests that it shipped with VS 15.5, and we're up to VS 15.5.2, so it must be public for somebody. But I'm working on a mac, and using dotnet core to build my project.</p>
  
  <p><code>dotnet --version</code> reports <code>2.1.2</code>. My project is super simple:</p>
  
  <pre><code>&lt;Project Sdk="Microsoft.NET.Sdk"&gt;
    &lt;PropertyGroup&gt;
      &lt;OutputType&gt;Exe&lt;/OutputType&gt;
      &lt;TargetFramework&gt;netstandard2.0&lt;/TargetFramework&gt;
      &lt;LangVersion&gt;latest&lt;/LangVersion&gt;
    &lt;/PropertyGroup&gt;
  &lt;/Project&gt;
  </code></pre>
  
  <p>And yet, for all I do, I can't reference <code>System.Span&lt;T&gt;</code>. What am I missing?</p>