Use the interfaces in a .NET Core 3.1 project

[janniksam]

So, I was looking for an IAsyncEnumerable alternative, that does work under .NET Standard 1.4 and found this library.

However, when I reference my consuming .NET Core 3.1 test, it gives me

Error CS7069 Reference to type 'IAsyncEnumerator<>' claims it is defined in 'AsyncEnumerable', but it could not be found.

or when I use IAsyncEnumerable

Error CS7069 Reference to type 'IAsyncEnumerator<>' claims it is defined in 'AsyncEnumerable', but it could not be found.

The error makes sense to me, because .NET Core 3.1 does support async streaming by default. Is there a way to use it in a .NET Core 3.1 test project anyways? (I would like to not change anything in my consuming project for this)