Go (Golang): Novice to Pro Guide

1. Novice Level (The Basics)

1.1 Introduction

• What is Go? Statically typed, compiled, designed by Google for simplicity and concurrency.
• Setup: Install Go, set GOPATH (or use Modules), go run main.go.

1.2 Syntax & Variables

• Packages: package main
• Imports: import "fmt"
• Variables: var x int = 10 or short declaration x := 10.
• Types: bool, string, int, float64.
• Constants: const Pi = 3.14.

1.3 Control Flow

• if, else (no parentheses around condition).
• switch (no need for break).
• for (the only loop in Go: for i := 0; i < 10; i++, for condition, for (infinite)).

1.4 Functions

• func add(x int, y int) int { return x + y }
• Multiple return values: func swap(x, y string) (string, string)
• Named return values.

2. Intermediate Level (Data Structures & Methods)

2.1 Arrays & Slices

• Arrays: Fixed size [2]string.
• Slices: Dynamic []int. make([]int, 5). append(slice, elem).
• Slicing: s[1:4].

2.2 Maps

• Key-Value pairs: make(map[string]int).
• delete(m, key).
• Checking existence: val, ok := m["key"].

2.3 Pointers

• & (address of), * (dereference).
• Passing by reference vs value.

2.4 Structs & Methods

• type Person struct { Name string; Age int }.
• Methods (receivers): func (p *Person) Greet().
• No classes, but composition/embedding.

2.5 Interfaces

• Implicit implementation (duck typing).
• type geometry interface { area() float64 }.
• Empty interface interface{} (Any type).

3. Advanced Level (Concurrency & Error Handling)

3.1 Concurrency (Goroutines & Channels)

• Goroutines: go f(x, y, z). Lightweight threads.
• Channels: Typed conduits. ch <- v (send), v := <-ch (receive).
• Buffered Channels.
• select statement for multiple channels.
• sync.Mutex and sync.WaitGroup.

3.2 Error Handling

• No exceptions. Errors are values.
• if err != nil { return err }.
• Custom errors (errors.New).
• defer, panic, recover.

3.3 Packages & Modules

• go.mod, go.sum.
• Exported names start with Capital letter.
• init() function.

4. Expert Level (Performance & Systems)

4.1 Testing

• testing package.
• func TestXxx(t *testing.T).
• Benchmarks: func BenchmarkXxx(b *testing.B).

4.2 Reflection & Unsafe

• reflect package (runtime inspection).
• unsafe package (careful!).

4.3 Web Development

• net/http package.
• Middleware patterns.
• JSON marshalling/unmarshalling (encoding/json).

4.4 Tooling & Best Practices

• gofmt (formatting).
• go vet (linting).
• Context package (context.Context) for cancellation/timeouts.