Types and variables

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Goal

Declare values and know their types. After this page you will read every variable declaration you meet in the rest of the tier.

Prerequisites

• Hello world

The types you actually need now

Go is statically typed — every value has a type fixed at compile time. The standard library is large, but the ladder needs five categories:

• int — whole numbers, sized to your CPU (32 or 64 bit). Use this unless you have a specific reason not to.
• float64 — decimal numbers.
• bool — true or false.
• string — text, UTF-8 internally, immutable.
• Composite types — struct, slice, map. We meet structs and slices later in the ladder.

For the full list of numeric widths (int8, int16, uint32, etc.), see the Go spec on numeric types. You won't need them this tier.

Three ways to declare a variable

package main

import "fmt"

func main() {
	// 1. Short declaration — type inferred from the value.
	count := 3

	// 2. Explicit type — useful when the inferred type isn't what you want.
	var price float64 = 4.5

	// 3. Multiple variables at once.
	var first, last = "Aarav", "Patel"

	fmt.Println(count, price, first, last)
}

Run it:

go run main.go

Output:

3 4.5 Aarav Patel

:= is short declaration. It only works inside a function. At package level, use var.

For frontend developers

:= is roughly const with type inference — except Go variables are reassignable by default. var x = 1 is closer to let x = 1 in JS.

Next → Control flow