Go Learning - Session 1 & 2

What is Go?

Go (Golang) is a statically typed programming language created at Google.

Goals:

• Simple syntax
• Fast compilation
• Single executable deployment
• Garbage collection
• Built-in concurrency support
  Commonly used for:
• Backend services
• Cloud infrastructure
• DevOps tools
• Command-line applications
  Examples of software written in Go:
• Docker
• Kubernetes
• Terraform
• Prometheus

---

Structure of a Go Program

A minimal Go program:

package main
 
import "fmt"
 
func main() {
    fmt.Println("Hello")
}

package main

Marks the package as executable.

package main

Programs start execution from the main() function inside package main.

---

import

Imports another package.

import "fmt"

Similar concept to:

#include <stdio.h>

or

import sys

---

main()

Entry point of the program.

func main() {
}

---

Printing Output

fmt.Println("Hello")

Prints a line followed by a newline.

---

Variables

Explicit Declaration

var version float64 = 0.1

Type Inference

version := 0.1

Go automatically infers the type.
Short declaration (:=) is commonly used when the value is known immediately.

---

Println and Automatic Spaces

Example:

fmt.Println("Version ", version)

Output:

Version  0.1

Reason:

• First argument already ends with a space.
• Println() automatically inserts a space between arguments.

Preferred:

fmt.Println("Version", version)

---

Reading User Input

var age int
 
fmt.Print("Enter age: ")
fmt.Scanln(&age)

---

Why ’&’?

The & operator returns the address of a variable.
Scanln() needs a memory location where it can store the value entered by the user.

Similar to:

scanf("%d", &age);

---

Command-Line Arguments

Import:

import "os"

Arguments:

os.Args

Example:

myprogram hello world

Contents:

os.Args[0]

Program name

os.Args[1]

First argument

os.Args[2]

Second argument

---

Basic Command Validation

if len(os.Args) < 2 {
    fmt.Println("Usage: myprogram <command>")
    return
}

Check the first argument:

command := os.Args[1]

Example:

if command == "hello" {
    fmt.Println("Hello")
} else {
    fmt.Println("Unknown command")
}

---

Concepts Learned

Packages

package main

Imports

import "fmt"
import "os"

Functions

func main() {
}

Variables

var name string
 
name := "Alice"

Pointers (Basic Usage)

&variable

Used when another function needs access to the variable’s memory location.

User Input

fmt.Scanln()

Command-Line Arguments

os.Args

---

Session Summary

Topics covered:

• Structure of a Go program
• Packages
• Imports
• Functions
• Variables
• Type inference
• Console output
• Console input
• Pointers for input
• Command-line arguments

Practical result:

• Built and executed a Go application
• Accepted user input
• Processed command-line arguments
• Implemented simple command selection logic

---

Next Topics

• Functions
• Multiple source files
• Packages
• Structs
• Error handling
• Building larger command-line applications
• Go Learning - Session 3