Introduction to Go

What you need to know to start programming in Go

Last edited on Oct 23, 2021 by Dave Stearns

Back in 2009 Google released the first version of their new open-source systems programming language known as Go. Since then it has grown significantly in popularity, especially among those working on newer network services and tools. This rise is understandable, as the language combines the performance of fully-compiled languages like C and C++ with the ease and safety of garbage-collected languages like Java and C#, while offering a sparse and simple syntax like Python and Swift. The accompanying tools and IDE plug-ins provide a fluid and consistent coding experience, while also encouraging best practices like automated testing.

What is Go?

Go is a statically-typed, fully-compiled, statically-linked, garbage-collected, concurrent systems programming language. Let's break that down a bit:

  • Statically-Typed means that all variables and parameters are declared with a specific data type, so the compiler can verify at compile-time that all values assigned to those variables/parameters are of the correct type. For example, a statically-typed language makes it impossible to pass a string to a function parameter that expects an integer without first converting that string to an integer and handling any errors that might occur. Although this may seem inflexible, it tends to avoid numerous problems and errors that might occur at runtime in languages with more dynamic typing, such as JavaScript. Static typing makes your programs much more predictable, and allows the compiler to catch all kinds of errors at compile-time.
  • Fully-Compiled means that Go programs are compiled all the way down to native machine code for a particular chip architecture, so when they execute, no further interpretation or compilation is necessary (see graphic below). Languages like JavaScript and Python are interpreted at run-time, meaning that a runtime engine parses, compiles, and executes your source code as the program runs. Languages like Java and C# compile your source code at compile-time, but they compile it to an intermediate virtual machine code that still has to be translated at run-time into the actual machine code supported by the chip architecture on which the program is running. Go programs, like C and C++ programs, are fully-compiled so they require no run-time engine and no run-time translation. In practical terms, this means that Go programs will typically run much faster than Python or JavaScript programs, especially if your program makes heavy use of the system CPU or RAM.
  • Statically-Linked means that all the code you use from Go's standard library, as well as third-party packages, is compiled into your built executable. When combined with the fully-compiled quality, this means that distributing a Go program to another machine is literally as simple as copying a single file. Go also supports compiling your program for other architectures, so you can produce a Windows executable on your Mac or a Linux executable on a Windows machine, and just copy that to the target computer.
  • Garbage-Collected means that you don't have to explicitly free memory that your program allocates, just like in Java. Older languages like C and C++ required developers to explicitly allocate and free memory, and if you forgot to, you leaked memory. For short-running programs this isn't so bad, as the operating system reclaims the leaked memory after your program exits, but for long-running programs like a web service, a small leak could amount to significant amounts of memory over time, ultimately causing your program to run out of memory and crash. Garbage collection is slightly less efficient than manual memory management, so a well-written C program will typically outperform a Go program, but not by an amount you'd typically notice except at extremely large scales.
  • Concurrent means that Go was designed from the start to support concurrent processing within a single executable. Go makes it easy to start multiple independent routines that take full advantage of multiple CPU cores. The basic Go web server provided in the standard library, uses this feature to process each HTTP request on its own concurrent "goroutine," enabling your services to transparently scale up to the number of CPU cores available on the current machine.
  • Systems Programming means that Go was designed for building system commands and network services, not graphical end-user applications. Although there are several third-party frameworks for building GUI applications, the standard library focuses on the tools and features you need to build comamnd-line utilities and network servers. Go is typically used to build Web API servers that are called by various kinds of clients, each written in the appropriate languages for the target platform (HTML/CSS/JavaScript for web clients; Swift for iOS native apps; Java for Android native apps).

Installing Go

To install Go on your development machine, follow the instructions below for your particular operating system.

MacOS

You can install Go on MacOS using either the Homebrew package manager, or the package installer on the Go downloads page.

If you installed a previous version of Go via their package installer, stick with that technique. If you haven't installed a previous version, I'd highly recommend installing Homebrew package manager and using that to install Go or any other command-line utility you might need.

If you want to install Go using Homebrew, run this command:

brew install go

You can then upgrade Go at any time in the future using the command

brew upgrade go

Windows

On Windows, download and run the MSI file from the Go downloads page. See their documentation on the MSI installer for details about what it does.

Linux

On Linux, download the latest tarball from the Go downloads page, and untar it into /usr/local. Then add /usr/local/go/bin to your PATH environment variable.

Configuring Go

Create the Go Workspace

Many of the Go tools assume a single "workspace" directory in which you keep your source code, and in which the tools compile and install packages. The typical place for this workspace directory is a directory named go inside your home directory (i.e., $HOME/go). If you're OK with this, create a directory inside your home directory named go. But you may put it somewhere else if you wish (e.g., $HOME/code/go).

Wherever you put your workspace directory, create two subdirectories inside it named src and bin. You will clone all your source repositories into the src branch, and the go install command will install your built executables to the bin directory.

In order for the Go tools to know where your workspace is, you need to define a persistent environment variable named GOPATH that is set to your workspace directory's path. This will also make it easier to refer to this workspace directory in other environment variables, such as your PATH.

Add Workspace Bin to Path

Since your built executables will be installed to $GOPATH/bin, you should also add that directory to your path. Update your PATH environment variable to include the $GOPATH/bin directory at the end.

Watch out for GOROOT

Older versions of Go also used an environment variable named GOROOT that was set to the directory containing the Go build tools. This is not needed anymore, and should only be used if you choose to install Go to some other location than its default. But if you have an older version installed that set this variable, and you install a new version to a different directory, you builds may fail. To see if this environment variable is set use echo $GOROOT. If it prints something other than a blank line, remove that persistent environment variable from your profile script.

Testing Your Installation

After installing and configuring the Go workspace, you can verify the installation by first executing:

go version

If you see the version information, all is well. If you get a "command not found" error, something went wrong. Verify that Go was installed and that your PATH environment variable was updated to include the installation directory (i.e., echo $PATH). Remember that adjustments to persistent environment variables defined in a profile script are not visible to existing command-line shells. Either open a new command-line window, or use the source command to re-run the profile script in your current terminal window.

Once you verify that go version prints version information, you can then test your workspace configuration by doing the following:

  • create a new directory at $GOPATH/src/testinstall
  • create a file in that directory named main.go and put the following code into it:
package main

import (
    "fmt"
)

func main() {
    fmt.Println("Hello world, go is installed!")
}
  • at the command line, execute the following:
cd $GOPATH/src/testinstall
go install

If the go install command didn't produce any errors, you are good to go! (warning: there will be many "go" puns throughout these tutorials). If you got an error, ensure that your GOPATH variable is set to your Go workspace directory path (echo $GOPATH).

The go install command compiled and installed your executable to the $GOPATH/bin directory. If you added that to your PATH environment variable as instructed above, you can run it by simply entering the name of the executable: testinstall on MacOS/Linux; or testinstall.exe on Windows.

# on MacOS/Linux
testinstall

# on Windows
testinstall.exe

Structure of the src Sub-Directory

Since all source code will go into the $GOPATH/src directory, Go defines a particular structure for this directory that will keep everything separated. The path for any cloned GitHub repo should be $GOPATH/src/github.com/username/reponame, where username is the GitHub user or organization who owns the repo, and reponame is the name of the repository. For example, the repo for these tutorials (drstearns/tutorials) should be cloned into $GOPATH/src/github.com/drstearns/tutorials.

If your repo is hosted on some other cloud service, replace the github.com part of the path with the domain name of your cloud service (e.g., bitbucket.org or gitlab.com).

Installing Packages and Tools

The core Go tools and standard library offer quite a lot, but sometimes you will want to install other tools or packages written in Go. Since Go is fully-compiled for a particular chip architecture and operating system, the person supplying the tool/package must either provide builds for all the common platforms, or provide the source code. Since Go itself is open-source, most Go developers choose the latter approach: they put the source code for their tool/package in a repo, and tell you to download and install it using go get.

The go get tool can download a repo from most popular git hosting sites, compile the code, and install the resulting binary to the $GOPATH/bin(for tools) or $GOPATH/pkg (for libraries) directory. It accepts a path just like the path you should use for the source code under the src directory. For example, to download, build, and install the popular gocode tool, use this command:

go get github.com/nsf/gocode

Go Extensions for Editors and IDEs

The gocode tool provides rich statement completion while programming in Go, but to use it, as well as the other helpful coding assistance tools, you need to install the extension for your chosen editor or IDE. If you're using Visual Studio Code, their Go extension is fabulous.

Most of these add-ins will have a command to install all the various analysis tools (such as gocode) they need to run. In Visual Studio Code, open the command palette using Cmd+Shift+P on Mac (Ctrl+Shift+P on Windows) and type go: tools to find the go: Install/Update Tools command. Select that to run the command and it will use go get to install all of the various tools it needs to provide a rich coding experience. For other editors/IDEs, see their add-in reference for details on how to install the various tools.

Searching for Help

Pro Tip: If you run into problems, use the term "golang" when searching for solutions. The word "Go" is far too common and ambiguous, so most help forums will use the more indexable term "golang" instead.

Learn the Language

Now that you know what Go is, and have a working installation, continue on by learning the basics of the language!