Bingo!

gistfile1.txt

// lightbulb
public static async Task<TOut> MapAsync<TIn,TOut>(this Task<TIn> @this, Func<TIn, Task<TOut>> fn) => await fn(await @this);

// all permutations
public static TOut Map<TIn,TOut>(this TIn @this, Func<TIn, TOut> fn) => fn(@this);
public static async Task<TOut> MapAsync<TIn,TOut>(this TIn @this, Func<TIn, Task<TOut>> fn) => await fn(@this);
public static async Task<TOut> MapAsync<TIn,TOut>(this Task<TIn> @this, Func<TIn, TOut> fn) => fn(await @this);
public static async Task<TOut> MapAsync<TIn,TOut>(this Task<TIn> @this, Func<TIn, Task<TOut>> fn) => await fn(await @this);

// example
var x = 1;
var i = await x.Map(H).MapAsync(G).MapAsync(F); // i == 9

Hi, im interested in using this, can you please tell me how to make it work on tampermonkey?
email me @ marineoverlord@gmail.com