dependsOn.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Net.Http;
using Newtonsoft.Json;
using static Bullseye.Targets;

namespace bulltest
{
    class Program
    {
        private static decimal _exchangeRate;
        private static HttpClient _httpClient = new HttpClient();
        
        static void Main(string[] args)
        {
            Target("getexchangerate", async () => {
                var response = await _httpClient.GetStringAsync("https://api.exchangeratesapi.io/latest?base=CAD&symbols=USD");
                var data = JsonConvert.DeserializeObject<ApiData>(response);
                _exchangeRate = data.Rates["USD"];

                Console.WriteLine($"Rate: {_exchangeRate}");
            });

            Target("saveexchangerate", DependsOn("getexchangerate"), async () => {
                File.WriteAllText("currentRate.txt", _exchangeRate.ToString());
            });

            RunTargets(args);
        }
    }

    public class ApiData
    {
        public string Base {get;set;}
        public DateTime Date {get;set;}
        public Dictionary<string, decimal> Rates {get;set;}
    }
}