zaahidali / Learn-go-language

Learn Go Language by doing projects

Go Programming Essentials

Table of Contents

• Overview
• Introduction to Go
• Pros and Cons
• Basic Code Syntax
• Go Print Statements
• Go Format Specifiers
• String in Go
• String methods
• Slice in Go
• Slice methods
• Array vs Slice
• Go map
• Projects in Repository

Overview

Welcome to the Go Practice Document, where we'll explore the features and benefits of the Go programming language. This document aims to provide a professional overview of Go and highlight its important aspects.

Introduction to Go

Go is a statically typed programming language that compiles code into binary executables. It offers several key advantages that make it a popular choice among developers:

Pros and Cons

• Pros:

  • Statically Typed Language:
    • Type checks before compilation
    • Variable types are known before compilation like C, C++ & Java
  • Efficient Memory Management:
    • Fast and reliable
    • Great garbage collector for memory management
  • Extensive Standard Library:
    • Includes packages for HTTP, JSON, file I/O, and more
    • Reduces the need for external dependencies
  • Cross-Compilation:
    • Code can be compiled for different platforms without hassle
  • Concurrency:
    • Uses goroutines and channels for lightweight and efficient concurrency

• Cons:

  • Smaller Community compared to other languages/frameworks
  • Limited GUI Support
  • Smaller Libraries compared to languages like Ruby
  • Minimalistic Syntax

Basic Code Syntax

To provide a taste of Go, here's an example of the classic "Hello, World!" program in Go:

package main

import "fmt"

func main() {
    fmt.Println("Hello, World!")
}

Output:

Hello, World!

Data Types

Type	Description	Examples
int	Integer numbers.	7123, 0, -5, 7023
float	Numbers with decimal points.	20.2, 500.123456, -34.23
complex	Complex numbers.	2+4i, -9.5+18.3i
string	Sequence of characters.	"Hello World!", "1 is less than 2"
bool	Either true or false.	true, false
byte	A byte (8 bits) of non-negative integers.	2, 115, 97
rune	Used for characters. Internally used as 32-bit integers.	'a', '7', '<'

Go Print Statements

The Go programming language provides several print statement options that allow you to output text and values to the console. Here are three commonly used print statements in Go:

1. fmt.Println(): This statement prints the given arguments to the console, adding a new line after each print.

2. fmt.Print(): This statement prints the given arguments to the console without adding a new line. Subsequent prints will be displayed on the same line.

3. fmt.Printf(): This statement provides more control over the output by using format specifiers. It allows you to format and print values based on their type.

Example 1: fmt.Println()

package main

import "fmt"

func main() {
    fmt.Println("Hello, World!")
    fmt.Println("Hello, Sparta!")
}

Output:

Hello, World!
Hello, Sparta!

Example 2: fmt.Print()

package main

import "fmt"

func main() {
    fmt.Print("Hello ")
    fmt.Print("Sparta!")
}

Output:

Hello Sparta!

Example 3: fmt.Printf()

package main

import "fmt"

func main() {
    fmt.Printf("%s\n", "Hello, Sparta!")
    fmt.Printf("%d\n", 12345)
    fmt.Printf("%g\n", 12.50)
    fmt.Printf("%t\n", true)
}

Output:

Hello, Sparta!
12345
12.50
true

In the last example, we used format specifiers such as %s for strings, %d for integers, %g for floating-point numbers, and %t for booleans. The \n represents a new line character, which adds a line break after each print statement.

These print statements are essential for displaying output and debugging in Go, allowing you to communicate with the user and inspect the values of variables during program execution.

Go Format Specifiers

Type	Format Specifier
Integer	%d
Float	%g
String	%s
Boolean	%t
Character	%c
Hexadecimal	%x
Scientific notation	%e
Octal	%o
Pointer	%p
Width	%*d

String in Go

• A string in Go is a sequence of bytes.
• Strings are enclosed in double quotes ("like this") or backticks (`like this`).
• Strings in Go are immutable, meaning they cannot be changed once created.
• Go provides a rich set of string manipulation functions in the strings package for tasks like searching, replacing, splitting, and more.
• Strings can be compared using the == or != operators for equality or inequality.

String Methods

Method	Description	Example
Compare()	Compares two strings lexicographically	"abc".Compare("abd") // returns -1"
Contains()	Returns true if a string contains another string	"abcdef".Contains("cd") // returns true"
ToUpper()	Converts a string to uppercase	"hello world".ToUpper() // returns "HELLO WORLD"
ToLower()	Converts a string to lowercase	"Hello World".ToLower() // returns "hello world"
Replace()	Replaces all occurrences of a substring with another substring	"hello world".Replace("world", "everyone") // returns "hello everyone"
Split()	Splits a string into an array of substrings based on a separator string	"hello,world".Split(",") // returns ["hello", "world"]"
Join()	Joins an array of substrings into a single string using a separator string	strings.Join([]string{"hello", "world"}, ",") // returns "hello,world"

String Formatting

Specifier	Description	Example
%s	Formats a string	fmt.Sprintf("Name: %s", name)
%d	Formats an integer	fmt.Sprintf("Age: %d", age)
%f	Formats a floating-point number	fmt.Sprintf("Price: %.2f", price)
%t	Formats a boolean value	fmt.Sprintf("Is available: %t", isAvailable)

Example Code

package main

import (
    "fmt"
    "strings"
)

func main() {
    // Define a string variable
    message := "hello world"

    // Compare two strings
    result := strings.Compare("abc", "abd")
    fmt.Println(result) // Output: -1

    // Check if a string contains another string
    result = strings.Contains(message, "world")
    fmt.Println(result) // Output: true

    // Convert a string to uppercase
    result = strings.ToUpper(message)
    fmt.Println(result) // Output: HELLO WORLD

    // Convert a string to lowercase
    result = strings.ToLower(message)
    fmt.Println(result) // Output: hello world

    // Replace all occurrences of a substring with another substring
    result = strings.Replace(message, "world", "everyone", -1)
    fmt.Println(result) // Output: hello everyone

    // Split a string into an array of substrings
    resultArray := strings.Split(message, " ")
    fmt.Println(resultArray) // Output: [hello world]

    // Join an array of substrings into a single string
    result = strings.Join(resultArray, ",")
    fmt.Println(result) // Output: hello,world
}

Slice in Go

• A slice in Go is a variable-size sequence of elements that provides a more flexible and powerful alternative to arrays.
• Slices are built on top of arrays and provide a dynamic view into the underlying array.
• Unlike arrays, slices can grow or shrink in size as needed, allowing for more efficient memory usage.
• Slices are represented by a three-part structure: a pointer to the underlying array, a length indicating the number of elements in the slice, and a capacity representing the maximum number of elements the slice can hold.
• Slices are widely used in Go to work with collections of data, such as lists, buffers, or dynamic arrays.

Example: Working with Slices

package main

import "fmt"

func main() {
    // Create a slice
    numbers := []int{1, 2, 3, 4, 5}

    // Accessing elements of a slice
    fmt.Println(numbers[0]) // Output: 1
    fmt.Println(numbers[2]) // Output: 3

    // Modifying elements of a slice
    numbers[1] = 10
    fmt.Println(numbers) // Output: [1 10 3 4 5]

    // Slicing a slice
    slice := numbers[2:4]
    fmt.Println(slice) // Output: [3 4]
}

Slice Methods

Method	Description	Example
append()	Adds elements to a slice.	slice = append(slice, 4, 5)
copy()	Copies elements from one slice to another.	copy(destination, source)
DeepEqual()	Compares two slices for equality.	isEqual := reflect.DeepEqual(slice1, slice2)
len()	Returns the length of a slice.	length := len(slice)

Go Array vs Slice

Feature	Array	Slice
Definition	Fixed-size sequence of elements	Variable-size sequence of elements
Syntax	var arr [size]Type	var slc []Type
Length	Fixed, cannot change	Can change, dynamic
Capacity	Same as length	Can be larger than the length
Indexing	arr[i]	slc[i]
Creation	arr := [3]int{1, 2, 3}	slc := []int{1, 2, 3}
Resizing	Not possible	Possible using append or copy
Creating from an array	N/A	arr[start:end]
Underlying structure	Plain array	Reference to an array
Memory usage	Less (in-place storage)	More (reference + metadata)

• When passing an array to a function, Go makes a copy of the array, and the function works on the copy. So, any modifications to the array inside the function do not affect the original array in the calling function.
• On the other hand, when passing a slice to a function, Go passes a reference to the underlying array, which means that the function can modify the original array.

Here's an example demonstrating the differences:

package main

import (
	"fmt"
)

func modifyArray(arr [3]int) {
	arr[0] = 100
	fmt.Println("Inside modifyArray:", arr)
}

func modifySlice(slc []int) {
	slc[0] = 100
	fmt.Println("Inside modifySlice:", slc)
}

func main() {
	arr := [3]int{1, 2, 3}
	slc := []int{1, 2, 3}

	fmt.Println("Before modifyArray:", arr)
	modifyArray(arr)
	fmt.Println("After modifyArray:", arr)

	fmt.Println("\nBefore modifySlice:", slc)
	modifySlice(slc)
	fmt.Println("After modifySlice:", slc)
}

OUTPUT

Before modifyArray: [1 2 3]
Inside modifyArray: [100 2 3]
After modifyArray: [1 2 3]

Before modifySlice: [1 2 3]
Inside modifySlice: [100 2 3]
After modifySlice: [100 2 3]

In summary, when passing an array to a function, you're working with a copy, while when passing a slice, you're working with a reference to the original data. This is the primary difference when passing arrays and slices to functions in Go.

Go Map

Go maps are a built-in data structure that associate keys with values. They are similar to dictionaries in Python or hash tables in other programming languages. Some key features of Go maps include:

• Dynamic size: Maps in Go can grow or shrink in size as needed.
• Unordered: The order in which elements are stored in a map is not guaranteed, and iterating over a map may yield different orders.
• Reference type: Maps are reference types, which means that when you assign a map to another variable, they both point to the same underlying data. Modifying one will affect the other.
• Zero value: The zero value of a map is nil. A nil map has no keys, nor can keys be added.

Here's a summary of common map operations in Go:

• Create a map: To create a map, you can use the make function or initialize it with key-value pairs.
• Add/Update an entry: To add or update a key-value pair in the map, use the assignment operator (=).
• Delete an entry: To remove a key-value pair from the map, use the delete function.
• Get an entry: To retrieve the value of a key in the map, use the index operator ([]).
• Check if key exists: To verify if a key is in the map, use the , ok idiom when getting an entry.
• Length of the map: To get the number of entries in the map, use the len function.
• Iterate over the map: To loop through the map's key-value pairs, use the range keyword in a for loop.

Operation	Description	Example
Create a map	Initialize a new map	ages := make(map[string]int)
Create a map with values	Initialize a map with key-value pairs	ages := map[string]int{"John": 30, "Jane": 28}
Add an entry	Add a key-value pair to the map	ages["Alice"] = 25
Update an entry	Update the value of a key in the map	ages["John"] = 31
Delete an entry	Remove a key-value pair from the map	delete(ages, "John")
Get an entry	Retrieve the value of a key in the map	age := ages["John"]
Check if key exists	Verify if a key is in the map	age, ok := ages["John"]; if ok { ... }
Length of the map	Get the number of entries in the map	count := len(ages)
Iterate over the map	Loop through the map's key-value pairs	for key, value := range ages { ... }

Projects in the Repository

This repository also contains several projects that you can explore and use. Each project focuses on a different aspect of software development. Here is a list of the projects included along with a brief explanation:

• blog_post_orm_system: A blog post management system with an ORM (Object-Relational Mapping) approach.
• Updated migrations of blog_post_orm_system: Updated migrations for the blog post management system using ORM.
• budget_management_system_orm: A budget management system implemented using an ORM approach.
• education-management-system: A system for managing educational resources and information.
• library_management_api: An API for managing library resources and operations.
• simple_blog_api: A simple API for creating and managing blog posts.
• task_management_api_graphql: An API for managing tasks using GraphQL.
• task_manager_api: An API for managing tasks and tracking progress.
• task_manager_api_with_bun: An API for task management using the Bun ORM.
• task_tracker_api_with_graphql_and_bun: An API for tracking tasks using GraphQL and the Bun ORM.

Each project has its own README file in its respective repository. You can navigate to each project's repository to find more information about the project, its purpose, and instructions on how to use it. Feel free to explore and utilize these projects according to your requirements.