Hello world in Go

Every programming language career starts by writing Hello World program. Lets do it in Go.

Create a new folder called hello-world
Create a new file in it called hello.go

mkdir hello-world
cd hello-world
touch hello.go

Now write following code in it

package main

import "fmt"

func main() {
    fmt.Println("Hello, world!")
}

Run the program with following shell script go run hello.go .

Writing your first test

Go comes with built in test setup, this is a big deal if you are coming from other programming language where you need to setup your test, choose from different testing frameworks.

But how do we test the above code? Before writing a test case it is a good practice to separate your domain logic from the outside world (side effects). So lets do that first.

// main.go

package main

import "fmt"

func Hello() string {
    return "Hello, world!"
}

func main() {
    fmt.Println(Hello())
}

func keyword is used to create a function in Go. we named our function Hello() and we said this function should return string. Because Go is strongly typed language, this will helps us catch errors in compile time and our editor will help us fix them before even executing the program.

Lets create another file called hello_test.go and start writing our first test for our Hello function.

package main

import "testing"

func TestHello(t *testing.T) {
    got := Hello()
    expected := "Hello, world!"

    if got != expected {
        t.Errorf("expected %q got %q", expected, got)
    }
}

Few conventions in writing tests

Test file name should xxx_test.go in our case hello_test.go
The test function must start with the word Test in our case TestHello
The test function takes one argument only t *testing.T
In order to use the *testing.T type, you need to import import "testing".

Please note that, In the Go Installation and IDE Setup section, you'll find detailed setup instructions for both Visual Studio Code and Neovim. Once your IDE is configured correctly, it can efficiently handle the automatic import of necessary modules, simplifying your development process.

Go modules

Now that our test is ready you can run your test by typing go test in your terminal

$ go test
go: go.mod file not found in current directory or any parent directory; see 'go help modules'

If you see go.mod related problem, that means you are running go 1.16 or later, Go has a new module changes, you can read more about it Go Modules.

All you need to type is go mod init hello in your terminal followed by go mod tidy to fix this problem, and it will generate a go.mod file in your project.

$ go mod init hello      
go: creating new go.mod: module hello
go: to add module requirements and sums:
        go mod tidy
$ go mod tidy

If you are interested in what is generated in go.mod here is the content:

module hello

go 1.21.5

Now run go test command again and you will see your test is passing

$ go test    
PASS
ok      hello   0.001s

Next we will try to follow TDD approach to improve this hello world program.

Hello world in Go

Writing your first "Hello World" program in Go programming language.

Writing your first test

Few conventions in writing tests

Go modules