This expression should have type ‘unit’, but has type ‘ConsoleKeyInfo’

Solution:

Console.ReadKey() |> ignore

Explanation: Console.ReadKey() returns an object of type ‘ConsoleKeyInfo’ but you’re using it as a statement without assigning the return value to anything. So F# warns you that you’re ignoring a value. ignore takes any type and returns nothing. It could be defined like this:

let ignore _ = ()