Golang Backend Real-World (Part 3): Variables, Types & Constants

In this part of the Golang Backend Real-World series, we explore the foundational concepts that power every Go backend application: variables, data types, and constants.
Whether you’re building REST APIs, microservices, or CLI tools, these concepts appear everywhere in real-world Golang code.

1. Variables in Go

Variables store values that can change throughout the lifecycle of a program. Go is statically typed, meaning each variable has a specific type determined at compile time.

1.1 Declaring variables using `var`

var name string = "Leaf"
var age int = 30

This is the most explicit form of variable declaration in Go.

1.2 Declaring variables without initialization (zero values)

Go assigns a zero value when no initial value is provided:

var message string  // ""
var count int       // 0
var active bool     // false

This prevents undefined or null-type issues.

1.3 Short declaration (`:=`)

Commonly used inside functions for cleaner code:

title := "Golang Tutorial"
views := 102
enabled := true

Go infers the type automatically.

1.4 Declaring multiple variables

var a, b, c = 1, 2, 3

Or in block format:

var (
    username = "admin"
    attempts = 3
    isAdmin  = false
)

This is useful for grouping related variables.

2. Data Types in Go

Go provides a powerful type system optimized for both performance and readability. Here are the types most relevant to backend systems.

2.1 Numeric types

int, int8, int16, int32, int64
uint versions for unsigned integers
float32, float64 for decimal numbers

Example:

price := 19.99
quantity := 5

2.2 Strings

Go’s strings are UTF-8 encoded:

message := "Hello, Go!"

2.3 Boolean

isValid := true

2.4 Composite Types (important for backend systems)

Slice

roles := []string{"admin", "user"}

Map

config := map[string]string{
    "env": "production",
    "region": "ap-southeast-1",
}

Struct — core building block of backend models

type User struct {
    Name string
    Age  int
}

3. Constants in Go

Constants represent values that never change.

const AppName = "Codevivu.com"
const MaxConnections = 10

3.1 Using `iota` for enumerations

iota is a counter that increments automatically:

const (
    StatusPending = iota     // 0
    StatusApproved           // 1
    StatusRejected           // 2
)

This is useful for defining business logic states.

4. Summary

In Part 3, you learned:

Different ways to declare variables in Go
How zero values work
Core primitive and composite data types
How to define constants and enumerations using iota
Practical examples used in real backend systems