Chapter 2: Setup Go Lang and Hello World

Note: All Chapters Index (In case the reader needs to refer something back)

Go setup before version 1.11

Before we begin we should be aware of the difference in Go Lang before and after version 1.11.

Before version 1.11 we have a few environment variables which define the location and setup of the Go project.

1. GOROOT: It is a variable that defines where your Go SDK is located. You do not need to change this variable unless you plan to use different Go versions or install Go in a different directory than default (/usr/local/go)
2. GOPATH: It is the place where all Go projects should be located. For all *.go files to be able to locate and load other modules and dependencies they all must reside under this GOPATH. This means it defines the Go workspace and any new Go project should start within this workspace. But thankfully we don’t need it after version 1.11. But then how a Go project determines which place it should look into for Go project files? The answer is Go Modules, on a high level I would say now you can create a Go project anywhere and a file called go.mod in each project will take care of all the dependencies installed and modules referred.
3. GOBIN: The directory where go install and go get will place binaries after building main packages (Go is compiled language). Generally, this is set to somewhere on the system PATH as $GOPATH/binby default or $HOME/go/bin so that installed binaries can be run and discovered easily. We don’t have to set this explicitly in case you followed Chapter 1 or while creating binaries of project we can create them in same directory as project and refer the path to execute the binaries (I prefer later approach).

To get the value of all these env variables we have a command go env It prints all of the env variables related to Go. In order to see only a few env variables, append the name of variables after the command.

$ go env GOBIN GOPATH GOROOT
/home/himanshu/go
/usr/local/go

Note: I get these values from a Go project initialized with go mod init <project_name>(which I explained later in this chapter) Here GOBIN is empty and the other two lines show GOPATH and GOROOT respectively.

I am considering that we are not working with old version of Go lang. Thus we will not dig further here about old setup and see how we setup Go workspace with recent versions.

Go setup after version 1.11

Now let's begin with the setup of our Go lang project using Go Modules. This will be the standard way to set up any Go project.

• Create a directory anywhere for the project and move inside.

mkdir hello_world
cd hello_world

• Initialize a project with command go mod init <project_name>

$ go mod init hello_world
go: creating new go.mod: module hello_world

• A go.mod file is created and which contains the project name and version of Go this project is using. We are making this project for demo purpose only, But a more matured project should have module name as your_domain/account_name/repo_name in project name (e.g. github.com/user_name/hello_world). You can also refer this official Gorilla Mux Project and it’s go.mod file.
• Make a hello.go file and write below code in it

hello.go

• Here package main is the line which declare that file belong to main package. main package is mandatory to have in a Go Project because it tells the Go compiler that the package should compile as an executable program instead of a shared library. main package act as entry point in Go Project. In main package there should be one (and only one) file which belong to main package and have main() method in it. Commonly it is named as main.go but here we named it hello.go This main() method act as entry point for execution of program and executed first.
• Run the file using go run hello.go and you can see the output (Hello World).
• But we instead of just executing the file this way we can compile it first and then run. This is the how we do it in production, we compile the project into binaries and then send it into production to execute. To do this we will use go build hello.go command to build the binaries and ./hello to run the binary hello .

binary execution and direct run of hello.go

Congratulations !! on writing your first Go program. Keep going.

Read the comprehensive Go Lang course Here.
Feel free to reach Himanshu Patel for any doubt or help needed, contact info in the about section.