A 9-Hour Go Course for Beginners

⭐️ Contents ⭐️
(0:00:00) Intro
(0:03:17) Ch 1. Why write Go?
(0:27:39) Ch 2. Variables
(0:51:11) Ch 3. Functions
(1:16:58) Ch 4. Structs
(1:34:36) Ch 5. Interfaces
(2:00:26) Ch 6. Errors
(2:22:01) Ch 7. Loops
(2:48:21) Ch 8. Slices
(3:39:54) Ch 9. Maps
(4:06:19) Ch 10. Advanced functions
(4:31:03) Ch 11. Pointers
(4:48:02) Ch 12. Local development
(5:31:43) Ch 13. Channels & concurrency
(6:07:38) Ch 14. Mutexes
(6:30:56) Ch 15. Generics
(6:38:38) Ch 16. Quiz
(6:43:13) P1. RSS aggregator project
(6:53:43) P2. Chi router
(7:11:37) P3. Postgres database
(7:39:10) P4. Authentication w/ API keys
(8:18:28) P5. Many to many relationships
(8:39:13) P6. Aggregation worker
(9:05:28) P7. Viewing blog posts 

 string data = null;
var result = data ?? "value";

if (data == null)
{
    data = "value";
}
var result = data;

class Response
{
    public string Result { set; get; }
    public int Code { set; get; }
}

 
class WebRequest
{
    public Response GetDataFromWeb(string url)
    {
        // ...
        return new Response { Result = null };
    }
}

 var webData = new WebRequest().GetDataFromWeb("https://www.dntips.ir/");
if (webData != null && webData.Result != null)
{
    Console.WriteLine(webData.Result);
}

 if (webData?.Result != null)
{
    Console.WriteLine(webData.Result);
}

 if (x != null)
{
   x.Dispose();
}

 x?.Dispose();

 var copy = OnMyEvent;
if (copy != null)
{
   copy(this, new EventArgs());
}

 OnMyEvent?.Invoke(this, new EventArgs());

 var code = webData?.Code;

 if (webData?.Code > 0)
{

}

 int count = response?.Results?.Count ?? 0;

 int? x = 10;
//var value = x?.Value; // invalid
Console.WriteLine(x?.ToString());

 if (response != null && response.Results != null && response.Results.Addresses != null
  && response.Results.Addresses[0] != null && response.Results.Addresses[0].Zip == "63368")
{

}

 if(response?.Results?.Addresses?[0]?.Zip == "63368")
{

}

 public void DoSomething(Customer customer)
{
    string address = customer?.Employees
                  ?.SingleOrDefault(x => x.IsAdmin)?.Address?.ToString();
    SendPackage(address);
}

 public void DoSomething(Customer customer)
{
   Contract.Requires(customer != null); 
   string address = customer.GetAdminAddress();
   SendPackage(address);
}

optionsBuilder.UseSqlServer(
   @"Server=(localdb)\mssqllocaldb;Database=Demo.Batching;Trusted_Connection=True;",
   options => options.MaxBatchSize(1)
);

public class SqlServerModificationCommandBatch : AffectedCountModificationCommandBatch
    {
        private const int DefaultNetworkPacketSizeBytes = 4096;
        private const int MaxScriptLength = 65536 * DefaultNetworkPacketSizeBytes / 2;
        private const int MaxParameterCount = 2100;
        private const int MaxRowCount = 1000;

    public class Blog
    {
        public int BlogId { get; set; }
        public string Name { get; set; }
        public string Url { get; set; }
    }

    public class BloggingContext : DbContext
    {
        public DbSet<Blog> Blogs { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer(
                @"Server=(localdb)\mssqllocaldb;Database=Demo.Batching;Trusted_Connection=True;"/*,
                options => options.MaxBatchSize(2)*/
                );
            optionsBuilder.EnableSensitiveDataLogging();
        }
    }

            using (var db = new BloggingContext())
            {
                db.GetService<ILoggerFactory>().AddProvider(new MyLoggerProvider());

                // Modify some existing blogs
                var existing = db.Blogs.ToArray();
                existing[0].Url = "http://sample.com/blogs/dogs";
                existing[1].Url = "http://sample.com/blogs/cats";

                // Insert some new blogs
                db.Blogs.Add(new Blog { Name = "The Horse Blog", Url = "http://sample.com/blogs/horses" });
                db.Blogs.Add(new Blog { Name = "The Snake Blog", Url = "http://sample.com/blogs/snakes" });
                db.Blogs.Add(new Blog { Name = "The Fish Blog", Url = "http://sample.com/blogs/fish" });
                db.Blogs.Add(new Blog { Name = "The Koala Blog", Url = "http://sample.com/blogs/koalas" });
                db.Blogs.Add(new Blog { Name = "The Parrot Blog", Url = "http://sample.com/blogs/parrots" });
                db.Blogs.Add(new Blog { Name = "The Kangaroo Blog", Url = "http://sample.com/blogs/kangaroos" });

                db.SaveChanges();
            }

Executed DbCommand (41ms) [Parameters=[@p1='57', @p0='http://sample.com/blogs/dogs' (Size = 4000), @p3='58', @p2='http://sample.com/blogs/cats' (Size = 4000), @p4='The Horse Blog' (Size = 4000), @p5='http://sample.com/blogs/horses' (Size = 4000), @p6='The Snake Blog' (Size = 4000), @p7='http://sample.com/blogs/snakes' (Size = 4000), @p8='The Fish Blog' (Size = 4000), @p9='http://sample.com/blogs/fish' (Size = 4000), @p10='The Koala Blog' (Size = 4000), @p11='http://sample.com/blogs/koalas' (Size = 4000), @p12='The Parrot Blog' (Size = 4000), @p13='http://sample.com/blogs/parrots' (Size = 4000), @p14='The Kangaroo Blog' (Size = 4000), @p15='http://sample.com/blogs/kangaroos' (Size = 4000)], CommandType='Text', CommandTimeout='30']
SET NOCOUNT ON;
UPDATE [Blogs] SET [Url] = @p0
WHERE [BlogId] = @p1;
SELECT @@ROWCOUNT;

UPDATE [Blogs] SET [Url] = @p2
WHERE [BlogId] = @p3;
SELECT @@ROWCOUNT;

DECLARE @inserted2 TABLE ([BlogId] int, [_Position] [int]);
MERGE [Blogs] USING (
VALUES (@p4, @p5, 0),
(@p6, @p7, 1),
(@p8, @p9, 2),
(@p10, @p11, 3),
(@p12, @p13, 4),
(@p14, @p15, 5)) AS i ([Name], [Url], _Position) ON 1=0
WHEN NOT MATCHED THEN
INSERT ([Name], [Url])
VALUES (i.[Name], i.[Url])
OUTPUT INSERTED.[BlogId], i._Position
INTO @inserted2;

SELECT [t].[BlogId] FROM [Blogs] t
INNER JOIN @inserted2 i ON ([t].[BlogId] = [i].[BlogId])
ORDER BY [i].[_Position];

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
   optionsBuilder.UseSqlServer(
     @"Server=(localdb)\mssqllocaldb;Database=Demo.Batching;Trusted_Connection=True;",
     options => options.MaxBatchSize(2)
    );
    optionsBuilder.EnableSensitiveDataLogging();
}

Executed DbCommand (17ms) [Parameters=[@p1='65', @p0='http://sample.com/blogs/dogs' (Size = 4000), @p3='66', @p2='http://sample.com/blogs/cats' (Size = 4000)], CommandType='Text', CommandTimeout='30']
SET NOCOUNT ON;
UPDATE [Blogs] SET [Url] = @p0
WHERE [BlogId] = @p1;
SELECT @@ROWCOUNT;

UPDATE [Blogs] SET [Url] = @p2
WHERE [BlogId] = @p3;
SELECT @@ROWCOUNT;

Executed DbCommand (18ms) [Parameters=[@p0='The Horse Blog' (Size = 4000), @p1='http://sample.com/blogs/horses' (Size = 4000), @p2='The Snake Blog' (Size = 4000), @p3='http://sample.com/blogs/snakes' (Size = 4000)], CommandType='Text', CommandTimeout='30']
SET NOCOUNT ON;
DECLARE @inserted0 TABLE ([BlogId] int, [_Position] [int]);
MERGE [Blogs] USING (
VALUES (@p0, @p1, 0),
(@p2, @p3, 1)) AS i ([Name], [Url], _Position) ON 1=0
WHEN NOT MATCHED THEN
INSERT ([Name], [Url])
VALUES (i.[Name], i.[Url])
OUTPUT INSERTED.[BlogId], i._Position
INTO @inserted0;

SELECT [t].[BlogId] FROM [Blogs] t
INNER JOIN @inserted0 i ON ([t].[BlogId] = [i].[BlogId])
ORDER BY [i].[_Position];

Executed DbCommand (34ms) [Parameters=[@p0='The Fish Blog' (Size = 4000), @p1='http://sample.com/blogs/fish' (Size = 4000), @p2='The Koala Blog' (Size = 4000), @p3='http://sample.com/blogs/koalas' (Size = 4000)], CommandType='Text', CommandTimeout='30']
SET NOCOUNT ON;
DECLARE @inserted0 TABLE ([BlogId] int, [_Position] [int]);
MERGE [Blogs] USING (
VALUES (@p0, @p1, 0),
(@p2, @p3, 1)) AS i ([Name], [Url], _Position) ON 1=0
WHEN NOT MATCHED THEN
INSERT ([Name], [Url])
VALUES (i.[Name], i.[Url])
OUTPUT INSERTED.[BlogId], i._Position
INTO @inserted0;

SELECT [t].[BlogId] FROM [Blogs] t
INNER JOIN @inserted0 i ON ([t].[BlogId] = [i].[BlogId])
ORDER BY [i].[_Position];

Executed DbCommand (15ms) [Parameters=[@p0='The Parrot Blog' (Size = 4000), @p1='http://sample.com/blogs/parrots' (Size = 4000), @p2='The Kangaroo Blog' (Size = 4000), @p3='http://sample.com/blogs/kangaroos' (Size = 4000)], CommandType='Text', CommandTimeout='30']
SET NOCOUNT ON;
DECLARE @inserted0 TABLE ([BlogId] int, [_Position] [int]);
MERGE [Blogs] USING (
VALUES (@p0, @p1, 0),
(@p2, @p3, 1)) AS i ([Name], [Url], _Position) ON 1=0
WHEN NOT MATCHED THEN
INSERT ([Name], [Url])
VALUES (i.[Name], i.[Url])
OUTPUT INSERTED.[BlogId], i._Position
INTO @inserted0;

SELECT [t].[BlogId] FROM [Blogs] t
INNER JOIN @inserted0 i ON ([t].[BlogId] = [i].[BlogId])
ORDER BY [i].[_Position];

• بسیاری از نرم افزارها و پروتکل‌ها هنوز 8 بیتی کار می‌کنند.
• اگر یک متن انگلیسی ارسال کنید، 8 بیت هم کافی است ولی در این حالت 32 بیت جابجا می‌شود؛ یعنی 4 برابر و در ارسال و دریافت و پهنای باند برایمان مشکل ایجاد می‌کند.

مقایسه‌ای بین نسخه‌های مختلف :

همانطور که می‌بینید UTF-8 برای کاراکترهای اسکی، از یک بایت و برای دیگر حروف از دوبایت و برای بقیه BMP‌ها از سه بایت استفاده میکند و در صورتی که کاراکتری در ناحیه مکمل supplementary باشد، از چهار بایت استفاده خواهد کرد. UTF-16 از دو بایت برای نمایش کاراکترهای BMP و از 4 بایت برای نمایش کاراکترهای مکمل استفاده می‌کند و در UTF-32 از 4 بایت برای همه کاراکترها یا کد پوینت‌ها استفاده می‌شود.

let add x y = x + y
let result = add 4 5
printfn "(add 4 5) = %i" result

let add x y = x + y
let result1 = add 4 5
let result2 = add 6 7
let finalResult = add result1 result2

let add x y = x + y
let result =add (add 4 5) (add 6 7)

let cylinderVolume radius length : float =
   
   let pi = 3.14159
   length * pi * radius * radius

let sign num =
    if num > 0 then "positive"
    elif num < 0 then "negative"
    else "zero"

let replace(str: string) =
    str.Replace("A", "a")

let addu1 (x : uint32) y =
    x + y

let (|>) x f = f x

let result = 0.5 |> System.Math.Cos

let add x y = x + y
let result = add 6 7 |> add 4 |> add 5

let result = add 6 7 |> add 4

let sub (a, b) = a - b
let subFour = sub 4

prog.fs(15,19): error: FS0001: This expression has type
int
but is here used with type
'a * 'b

let rec fib x =
match x with
| 1 -> 1
| 2 -> 1
| x -> fib (x - 1) + fib (x - 2)


printfn "(fib 2) = %i" (fib 2)
printfn "(fib 6) = %i" (fib 6)
printfn "(fib 11) = %i" (fib 11) 

(fib 2) = 1
(fib 6) = 8
(fib 11) = 89

let rec Even x =
   if x = 0 then true 
   else Odd (x - 1)
and Odd x =
   if x = 1 then true 
   else Even (x - 1)

let firstFunction x = x + 1
let secondFunction x = x * 2
let newFunction = firstFunction >> secondFunction
let result = newFunction 100

let sumOfDivisors n =
    let rec loop current max acc =

//شروع تابع داخلی

   if current > max then
            acc
        else
            if n % current = 0 then
                loop (current + 1) max (acc + current)
            else
                loop (current + 1) max acc

//ادامه بدنه تابع اصلی

 let start = 2
    let max = n / 2     (* largest factor, apart from n, cannot be > n / 2 *)
    let minSum = 1 + n  (* 1 and n are already factors of n *)
    loop start max minSum
 
printfn "%d" (sumOfDivisors 10)

  if current > max then
            acc
        else
            if n % current = 0 then
                loop (current + 1) max (acc + current)
            else
                loop (current + 1) max acc

open System
open System.Windows.Forms

let form1 = new Form()
form1.Text <- "XYZ"

[<STAThread>]
do
   Application.Run(form1)

public class TravelAgent
{
    public TravelAgent()
    {
        this.Bookings = new HashSet<Booking>();
    }

    public int AgentId { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Booking> Bookings { get; set; }
}

public class Booking
{
    public int BookingId { get; set; }
    public int AgentId { get; set; }
    public string Customer { get; set; }
    public DateTime BookingDate { get; set; }
    public bool Paid { get; set; }
    public virtual TravelAgent TravelAgent { get; set; }
}

<connectionStrings>
  <add name="Recipe3ConnectionString"
    connectionString="Data Source=.;
    Initial Catalog=EFRecipes;
    Integrated Security=True;
    MultipleActiveResultSets=True"
    providerName="System.Data.SqlClient" />
</connectionStrings>

protected void Application_Start()
{
    // Disable Entity Framework Model Compatibilty
    Database.SetInitializer<Recipe1Context>(null);

    // The bidirectional navigation properties between related entities
    // create a self-referencing loop that breaks Web API's effort to
    // serialize the objects as JSON. By default, Json.NET is configured
    // to error when a reference loop is detected. To resolve problem,
    // simply configure JSON serializer to ignore self-referencing loops.
    GlobalConfiguration.Configuration.Formatters.JsonFormatter
        .SerializerSettings.ReferenceLoopHandling =
        Newtonsoft.Json.ReferenceLoopHandling.Ignore;
    ...
}

public static void Register(HttpConfiguration config)
{
    config.Routes.MapHttpRoute(
      name: "ActionMethodSave",
      routeTemplate: "api/{controller}/{action}/{id}",
      defaults: new { id = RouteParameter.Optional });
}

internal class Program
{
    private HttpClient _client;
    private TravelAgent _agent1, _agent2;
    private Booking _booking1, _booking2, _booking3;
    private HttpResponseMessage _response;

    private static void Main()
    {
        Task t = Run();
        t.Wait();
        Console.WriteLine("\nPress <enter> to continue...");
        Console.ReadLine();
    }

    private static async Task Run()
    {
        var program = new Program();
        program.ServiceSetup();
        // do not proceed until clean-up is completed
        await program.CleanupAsync();
        program.CreateFirstAgent();
        // do not proceed until agent is created
        await program.AddAgentAsync();
        program.CreateSecondAgent();
        // do not proceed until agent is created
        await program.AddSecondAgentAsync();
        program.ModifyAgent();
        // do not proceed until agent is updated
        await program.UpdateAgentAsync();
        // do not proceed until agents are fetched
        await program.FetchAgentsAsync();
    }

    private void ServiceSetup()
    {
        // set up infrastructure for Web API call
        _client = new HttpClient {BaseAddress = new Uri("http://localhost:6687/")};
        // add Accept Header to request Web API content negotiation to return resource in JSON format
        _client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
    }

    private async Task CleanupAsync()
    {
        // call cleanup method in service
        _response = await _client.DeleteAsync("api/travelagent/cleanup/");
    }

    private void CreateFirstAgent()
    {
        // create new Travel Agent and booking
        _agent1 = new TravelAgent {Name = "John Tate"};
        _booking1 = new Booking
        {
            Customer = "Karen Stevens",
            Paid = false,
            BookingDate = DateTime.Parse("2/2/2010")
        };

        _booking2 = new Booking
        {
            Customer = "Dolly Parton",
            Paid = true,
            BookingDate = DateTime.Parse("3/10/2010")
        };
  
        _agent1.Bookings.Add(_booking1);
        _agent1.Bookings.Add(_booking2);
    }

    private async Task AddAgentAsync()
    {
        // call generic update method in Web API service to add agent and bookings
        _response = await _client.PostAsync("api/travelagent/update/",
            _agent1, new JsonMediaTypeFormatter());

        if (_response.IsSuccessStatusCode)
        {
            // capture newly created travel agent from service, which will include
            // database-generated Ids for each entity
            _agent1 = await _response.Content.ReadAsAsync<TravelAgent>();
            _booking1 = _agent1.Bookings.FirstOrDefault(x => x.Customer == "Karen Stevens");
            _booking2 = _agent1.Bookings.FirstOrDefault(x => x.Customer == "Dolly Parton");

            Console.WriteLine("Successfully created Travel Agent {0} and {1} Booking(s)",
            _agent1.Name, _agent1.Bookings.Count);
        }
        else
            Console.WriteLine("{0} ({1})", (int) _response.StatusCode, _response.ReasonPhrase);
    }

    private void CreateSecondAgent()
    {
        // add new agent and booking
        _agent2 = new TravelAgent {Name = "Perry Como"};
        _booking3 = new Booking {
            Customer = "Loretta Lynn",
            Paid = true,
            BookingDate = DateTime.Parse("3/15/2010")};
        _agent2.Bookings.Add(_booking3);
    }

    private async Task AddSecondAgentAsync()
    {
        // call generic update method in Web API service to add agent and booking
        _response = await _client.PostAsync("api/travelagent/update/", _agent2, new JsonMediaTypeFormatter());

        if (_response.IsSuccessStatusCode)
        {
            // capture newly created travel agent from service
            _agent2 = await _response.Content.ReadAsAsync<TravelAgent>();
            _booking3 = _agent2.Bookings.FirstOrDefault(x => x.Customer == "Loretta Lynn");
            Console.WriteLine("Successfully created Travel Agent {0} and {1} Booking(s)",
                _agent2.Name, _agent2.Bookings.Count);
        }
        else
            Console.WriteLine("{0} ({1})", (int) _response.StatusCode, _response.ReasonPhrase);
    }

    private void ModifyAgent()
    {
        // modify agent 2 by changing agent name and assigning booking 1 to him from agent 1
        _agent2.Name = "Perry Como, Jr.";
        _agent2.Bookings.Add(_booking1);
    }

    private async Task UpdateAgentAsync()
    {
        // call generic update method in Web API service to update agent 2
        _response = await _client.PostAsync("api/travelagent/update/", _agent2, new JsonMediaTypeFormatter());
        if (_response.IsSuccessStatusCode)
        {
            // capture newly created travel agent from service, which will include Ids
            _agent1 = _response.Content.ReadAsAsync<TravelAgent>().Result;
            Console.WriteLine("Successfully updated Travel Agent {0} and {1} Booking(s)", _agent1.Name, _agent1.Bookings.Count);
        }
        else
            Console.WriteLine("{0} ({1})", (int) _response.StatusCode, _response.ReasonPhrase);
    }

    private async Task FetchAgentsAsync()
    {
        // call Get method on service to fetch all Travel Agents and Bookings
        _response = _client.GetAsync("api/travelagent/retrieve").Result;
        if (_response.IsSuccessStatusCode)
        {
            // capture newly created travel agent from service, which will include Ids
            var agents = await _response.Content.ReadAsAsync<IEnumerable<TravelAgent>>();

            foreach (var agent in agents)
            {
                Console.WriteLine("Travel Agent {0} has {1} Booking(s)", agent.Name, agent.Bookings.Count());
            }
        }
        else
            Console.WriteLine("{0} ({1})", (int) _response.StatusCode, _response.ReasonPhrase);
    }
}