Gold, an experimental Go local docs server, Go docs generation tool, and code reader. NEW!
-- show type implemention relations --
-- show code statistics --
-- smooth code view experiences --
-- and more... --

The Go Toolchain

Currently, the tools in the official Go Toolchain (called Go Toolchain later) are the most used tools to develop Go projects. In Go 101 article series, all examples are compiled and verified with the standard Go compiler.

This article will introduce how to setup the Go development environment and how to run simple Go programs. Some tools of Go Toolchain will also be introduced.

Install Go Toolchain

Please download Go Toolchain and install it according to the instructions shown in the download page.

The version of a Go Toolchain release is consistent with the highest Go language version the release supports. For example, Go Toolchain 1.15.x supports all Go language versions from 1.0 to Go 1.15.

The path to the bin subfolder in Go Toolchain installation root path must be put in the PATH environment variable to execute the tools (mainly the go subcommands) provided in Go Toolchain without inputting their full paths. If your Go Toolchain is installed through an installer or with a package manager, the path to the bin subfolder may have been already set in the PATH environment variable automatically for you.

Earlier Go Toolchain versions might require GOROOT and GOPATH environment variables to be set. Recent Go Toolchain versions have no such requirements. The default value of the GOPATH environment variable is the path to the go folder under the home directory of the current user. GOPATH environment variable may list multiple paths.

There is a GOBIN environment variable which controls where the binary files generated by some go subcommands, such as the go install subcommand (see below), will be stored. If the environment variable is not set, the go command will use the path to bin subfolder in the first path specified in the GOPATH environment variable to store the generated binary files. The path to the folder for storing the binary files should be set in the PATH environment variable to run the binary files without specifying their full paths.

Before Go Toolchain 1.11, it is recommended to put all custom Go packages into the src subfolder of any path specified in the GOPATH environment variable, in particular when a Go project depends on some third party packages. Packages will be introduced in packages and imports later.

In Go Toolchain 1.11, an experimental feature, Go modules, is supported. The Go modules feature lets us put our Go projects freely in any folder. We can get more module releated information from this wiki page.

Note, since Go Toolchain 1.13, the Go modules feature becomes as the preferred mode (to the old GOPATH mode). The necessity and meaningfulenss of the GOPATH environment variable will be weakened much, even be abolished eventually. On the other hand, the importance of the GOBIN environment variable will be promoted, for there is still a need to store the binary files produced by some go subcommands.

The Simplest Go Program

Let's write a simple example and learn how to run simple Go programs.

The following program is the simplest Go program.
package main

func main() {

The words package and func are two keywords. The two main words are two identifiers. Keywords and identifiers are introduced in a coming article.

The first line package main specifies the package name (main here) of the source file.

The second line is a blank line for better readability.

The remaining code declares a function which is also called main. This main function in a main package specifies the entry point of a program. (Note that some other user code might be executed before the main function gets invoked.)

Run Go Programs

Go Toolchain requires that Go source code file to have the extension .go. Here, we assume the above source code is saved in a file named simplest-go-program.go.

Open a terminal and change the current directory to the directory which contains the above source file, then run
$ go run simplest-go-program.go

Nothing is output? Yes, this program outputs nothing.

If there are some syntax errors in the source code, then these errors will be reported as compilation errors.

If multiple source files are in the main package of a program, then we should run the program with the following command
$ go run .

Note, the go run command is not recommended to compile and run large Go projects. It is just a convenient way to run simple Go programs, like the ones in the Go 101 articles. For large Go projects, please use the commands go build or go install to build and create executable binary files instead.

More go Subcommands

The three commands, go run, go build and go install, only output code syntax errors (if any). They don't (try to) output code warnings (a.k.a., possible code logic mistakes). We can use the go vet command to check and report such warnings.

We can use the go fmt command to format Go source code with a consistent coding style.

We can use the go get command to get a remote third-party go package to local. go get requires the corresponding version control tool must be installed.

We can use the go test command to run tests and benchmarks.

We can use the go doc command to view Go documentation in terminal windows.

Since Go Toolchain 1.11, we can use the go mod command to manage dependencies.

We can use the go help aSubCommand command to view the help message for a specified sub command.

The go command run without any arguments shows the supported subcommands.

The Go 101 article series will not explain much more on how to use the tools provided in Go Toolchain. Please read the official documentation for details.

View Go Documentation in Browsers

We can view all kinds of Go documentation on the official Go website and package docs on

We can also install the godoc program by running go get -u, then run godoc -http=:9999 to start a local clone of Go official website at localhost:9999. The godoc tool can also be used to view docs of Go projects locally.

Another docs view tool is Gold, which is developed by me (Tapir Liu). Gold supports rich code reading experience and lists type implementation relations. We can run go get -u to install Gold. To utilize the GOPROXY setting in the installation process, currently (Go Toolchain 1.15), the GO111MODULE enviroment variable needs to be set as on before starting the installation. We can also clone Gold's source code, then run go install in the project directory to install Gold. After the installation, we can run gold std to read the docs of the standard packages.

The Go 101 project is hosted on Github. Welcome to improve Go 101 articles by submitting corrections for all kinds of mistakes, such as typos, grammar errors, wording inaccuracies, description flaws, code bugs and broken links.

If you would like to learn some Go details and facts every serveral days, please follow Go 101's official Twitter account: @go100and1.

The digital versions of this book are available at the following places:
Tapir, the author of Go 101, has spent 3+ years on writing the Go 101 book and maintaining the website. New contents will continue being added to the book and the website from time to time. Tapir is also an indie game developer. You can also support Go 101 by playing Tapir's games (made for both Android and iPhone/iPad):
Individual donations via PayPal and cryptocurrencies are welcome too:
Bitcoin: 1xucQbv5jujFPPwhyg395ri5yV71hx9g9
Ethereum: 0x5dc4aa2c2bbfaadae373dadcfca11b3358912212