1. What is array in Go?

In Golang, array is a collection of data with fixed length and type (emphasized on the word "fixed"). Since Go is a statiscally-typed language, once we assign a type or length to an array, it cannot be changed.

Here is an example of an array of 3 string value

s:=[3]string{"hello", "new", "world"}

2. Length and type of Go array

Before we come to declaring an array, we need to know its length and type.

Syntax

Length is put inside square bracket [] and type is written right next to it.

var s [3]string

Length value

Length can be both constant or constant expression like

var s [3+2]string

3. How to declare an array in Go?

There are several ways to declare/ instantiate an array in Go.

Using variable declaration

var s [3]string

Using array literal

s := [3]string{"hello", "new", "world"}

When we instantiate an array in this way, it will always contain 3 elements, even though we haven't declared it as the first place. Compared to using ellipsis in declaring array length:

Using ellipsis

s := [...]string{"hello", "new"}

The elements that we explicitly write out will determine the length of your array. In this case, the array contains only 2 elements. Whereas with constant length, even though we declare it with 2 elements, the rest will be filled with zero values of string, which is "" aka empty string.

s := [3]string{"hello", "new"}