public static Task<TDocument> FirstAsync<TDocument>(
	this IAsyncCursorSource<TDocument> source,
	CancellationToken cancellationToken = null
)

<ExtensionAttribute>
Public Shared Function FirstAsync(Of TDocument) ( 
	source As IAsyncCursorSource(Of TDocument),
	Optional cancellationToken As CancellationToken = Nothing
) As Task(Of TDocument)

[<ExtensionAttribute>]
static member FirstAsync : 
        source : IAsyncCursorSource<'TDocument> * 
        ?cancellationToken : CancellationToken 
(* Defaults:
        let _cancellationToken = defaultArg cancellationToken null
*)
-> Task<'TDocument>