Program Structure in GO

By Darío Rivera

Posted On 2023-06-05 in Go

In a previous post we saw the installation of Go in Linux, today let's see what elements we need to make any program in Go.

Initial structure

All Go programs start with the main function in the main package. Additionally, it is not necessary to end statements with ; (semicolon).

package main

import "fmt"

func main() {
    fmt.Printf("hello, world\n")
}

In the previous program, we can see that the first section of the program composed of the first line contains the declaration of the current package, which in our case is main. The second section of the program composed of the third line contains the declaration of the import paths that uses the reserved word import. Import paths basically load libraries (classes) from the core or from third parties. The third part of the program composed of the last three lines defines the main function which is the starting point of the program. To add more than one import path, you can add as many lines as needed.

import "fmt"
import "math/rand"

Or use the recommended syntax (factored).

import (
	"fmt"
	"math/rand"
)

Variables

The initial structure seen above is the initial scaffold for creating programs in Go. However, a program without variables is of little use. Variables in Go can be defined at both the package and function level.

package main

import "fmt"

var c, python, java bool

func main() {
	var i int
	fmt.Println(i, c, python, java)
}

Variables can be declared and initialized in the same statement as shown below.

var i, j int = 1, 2

When using the initializer, the variable type can be omitted, leaving it as follows:

var i, j = 1, 2

It is also possible to declare and initialize variables of different types.

var c, python, java = true, false, "no!"

If the variable declaration depends on an expression or is composed of many statements, the factored or block form can be used as follows:

var (
	isSomething  bool       = false
	MaxInt       uint64     = 1<<64 - 1
	z            complex128 = cmplx.Sqrt(-5 + 12i)
)

Finally, within a function it is possible to avoid the use of the reserved word var in the definition of variables by combining it with the short assignment declaration :=.

k := 3
c, python, java := true, false, "no!"

See you next time!.

Initial structure

Variables

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