Welcome To Golang By Example

Set up GO Workspace and Hello World Program

admin

This is the chapter 3 of the golang comprehensive tutorial series. Refer to this link for other chapters of the series – Golang Comprehensive Tutorial Series

Next Tutorial – Packages and Modules – Part 1
Previous Tutorial – GO Installation

Now let’s check out the current tutorial. Below is the table of contents for the current tutorial.

Overview

This is the third tutorial of the golang comprehensive tutorial series. Refer to this link for other chapters of the series.

In chapter one we saw an intro to Go and basic advantages of GO and in chapter 2 we have already seen how to install GO. It is now time to set up the workspace for GO and run our first hello world program.

GO Workspace

Before we proceed let’s understand some important GO ENV variables:

GOROOT

It is the location of your GO SDK. GO binary distribution assumes this location to be /usr/local/go for Linux/MAC platforms and  c:\Go for Windows. But GO SDK can also be installed in a custom location. In case it is installed to a custom location, then GOROOT should point to that directory.  GOROOT should only be set when installing GO to a custom location or when you want to maintain different versions of GO

For example if you have installed GO to the location ~/Documents/go on Linux/MAC platform, then make below entry to the ~/$HOME/.profile file.

export GOROOT=~/Documents/go
export PATH=$PATH:$GOROOT/bin

GOPATH

The discussion for GOPATH will revolve around whether you are using GO version 1.13 higher or lower. In version 1.13, GO introduced a new feature for dependency management called GO modules. Let’s first understand the legacy behavior of GOPATH and then we will discuss what has changed with respect to GOPATH after GO version 1.13.

Before GO version 1.13

The GOPATH env variable was used for resolving go imports statements as well as it also specifies the location of your GO workspace. It is the root of GO workspace. A dependency cannot be imported if it is not inside GOPATH. Hence earlier version required all your source code to be inside GOPATH. So basically GOPATH is used for

It contains the following folders

With Go version 1.13 or later

In version 1.13, GO announced a new feature of dependency management called GO modules. We will learn about this feature in upcoming tutorials. For now, you can imagine that with the new feature, GO doesn’t require putting all GO code in the Go workspace or in the $GOAPTH/src directory. You can create the directory anywhere and put your Go program there. Note that all legacy behavior of GOPATH is still valid for version 1.1.3 and higher.  Also note that with this new GO module feature, GO programs can be run in two ways. 

Set Up GOPATH.

If this env variable is unset, it defaults $HOME/go on Unix systems and %USERPROFILE%\go on Windows. If your workspace location is ~/Desktop/go, then make below entry to the ~/$HOME/.profile file. It is good idea to always have the GOPATH set up as GOPATH is used even with the introduction of modules

export GOPATH=~/Desktop/go

GOBIN

GOBIN env variable specifies the directory where go will place the compiled application binary after building the main package. It defaults to $GOPATH/bin or $HOME/go/bin if the GOPATH environment variable is not set. .  Also it is good idea to add GOBIN path to PATH env as well so that binary installed can be run without specifying full path of the binary. Set GOBIN in the ~/.$HOME/.profile file and add it to PATH as well.

export GOBIN=$GOPATH/bin
export PATH=$PATH:$GOBIN

Run Hello World

In this example, we will be creating our first hello world program. So far here is the value of GOROOT, GOPATH, and GOBIN.

echo $GOROOT will give installed directory for GO
echo $GOPATH will give ~/Desktop/go
echo $GOBIN will give ~/Desktop/go/bin

A typical program has .go file extension. Now let’s create a “Hello World” program. For that first create a directory named hello outside $GOPATH/src.  Since the project is getting creating outside $GOPATH/src we also need to create a go.mod file with import path as sample.com/hello .  We will look at the import path, go.mod file and module in detail in the upcoming tutorial. For now, let’s create a simple module so that we can see how the hello world program looks like in go. Use the below command for that

go mod init sample.com/hello

It will create go.mod file as below.

go.mod

module sample.com/hello

go 1.14

Now create file hello.go with below contents.

package main

import "fmt"

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

There are three different commands to run the above GO program. First cd to the ‘hello’ directory.

  1. ‘go install’

It will compile the program and place the binary at the $GOBIN folder. Type below command, Make sure you are in the hello directory which contains the hello.go file.

It will create a binary named hello in the $GOBIN directory. The name of the binary is same as last part of the import path of the module. The import path of the module is sample.com/hello and last part of import path is simply hello. Hence binary name will be hello in our case. Type hello on the terminal, it will give below output

Hello World

Output of ‘which hello’ will be ‘~/Desktop/go/bin/hello’ . Remember our GOBIN path was ‘~/Desktop/go/bin.’ Hence the binary hello was copied to this directory.

  1. ‘go build’

It will compile the program and place the binary in the current working directory. Type the below command

go build

In our case it will create the binary named ‘hello’  same as impbeside hello.go file. To run the binary type ‘./hello’ on the terminal. It will give below output

Hello World
  1. ‘go run hello.go’

This command will compile and then execute the binary. Type the below command.

go run hello.go

It will output

Hello World

Conclusion:

That all for this tutorial. Hope you have liked this article. please share feedback/mistakes/improvements in comments.

Next Tutorial – Packages and Modules – Part 1
Previous Tutorial – GO Installation