🐹 Go (Golang) Handbook

Overview

Go is a statically typed, compiled language designed at Google for simplicity, performance, and concurrency. It is widely used for cloud services, microservices, CLI tools, and DevOps tooling.

Version Go 1.21+  Paradigm Procedural, Concurrent  Typing Static

Core Concepts

Variables & Types

• var x int = 10 or short form x := 10
• Basic types: int, float64, string, bool, byte, rune
• Zero values — variables always initialized
• Type inference with :=

Control Flow

• if / else if / else (no parentheses required)
• for — only loop construct (covers while too)
• switch — no fallthrough by default
• defer — runs at function end

Functions

• Multiple return values: func divide(a, b int) (int, error)
• Named return values
• Variadic functions with ...
• First-class functions and closures

Concurrency

• goroutine — lightweight threads with go func()
• channel — typed communication between goroutines
• select — multiplex channel operations
• sync.WaitGroup, sync.Mutex for synchronization
• context package for cancellation

Key Packages & Tools

Category	Package / Tool
Web	net/http, Gin, Echo, Fiber
Testing	testing, testify
Database	database/sql, GORM
CLI	cobra, flag
Build/Deploy	go build, go mod, Docker

Common Interview Topics

• Goroutines vs OS threads
• Channel buffering and deadlocks
• Interfaces and duck typing
• Pointers vs values
• Error handling pattern (if err != nil)
• Go modules and dependency management
• Struct embedding vs inheritance