I have been trying to get the Web Crawler example to compile taken from Don's,Adam/s and Antonio's most excellent book. I am gertting a problem that I am not sure whether it is a problem with my version fo the compiler or not. I am using version 1.9.3.7.
in the function collectLinks (see below) the result tht I get back from the async block to assign to the variable html is an Async<string> instead of a string. I thought the purpose of the return! statement was to unwrap the contained variable from the monadic wrapper. When I try to use it as the parameter for the getLinks function of course it tells me that it cannot use an Async<string> where it expects a string.

I am at a loss.

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let collectLinks (url:string) =
	async {
		let html = async {
					use! holder = webRequestGate.AcquireAsync()
					let req = WebRequest.Create(url, Timeout = 5)
					use! response = req.GetResponseAsync()
					use reader = new StreamReader(response.GetResponseStream())
					return! reader.ReadToEndAsync() }
		let links = getLinks html
		do printfn "finished reading %s, got %d links" url (List.length links)
		return links
	}

Any help would be greatly appreciated.
David