Please offer me helps : "How do I cancel other operations in Async.Parallel when one operation returns"

[Xyncgas]

I am trying to make http requests that may return something or post something
Let's say

    type HttpOperation =
    | Get of Async<string>
    | Put of Async<unit>

I have a bunch of Get or Put in seq<HttpOperation>, and I wanted to execute them all together for efficiency via Async.Parallel

async {
    let! results = (mySeq :Async<string> seq) |> Async.Parallel
}

but instead of getting results, I wanted the first result available and cancel other operations in Async.Parallel, now how do I do the cancelation?