The Official Go SDK

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.)

The official Go SDK 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.

Note: if multiple source files are in the main package of a program, then we should run the program with the following command

$ go run *.go

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 instead.

More go Subcommands

The three commands, go run, go build and go install, will only show code syntax errors (if any). They don't (try to) show 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 clone and checkout a remote third-party go package repository. go get requires the corresponding version control tool must be installed. If the command succeeds, the third-party go package will be put in the src folder under the first path specified in the GOPATH environment variable.

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

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

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

Since Go SDK 1.11, we can use the go mod command to package dependencies. Please run go help mod for more details.

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 by the official Go SDK. Please read the official documentations for details.

View Go Documentations In Browsers

We can view all kinds of Go documentations at the official Go website golang.org.

We can also run godoc -http=:9999 to start a local clone of the official website at localhost:9999.

Please note that, for Go SDK 1.10, if the GOROOT environment variable is unset, we must specify the goroot flag when running the local godoc server, e. g. godoc -http=:9999 -goroot path/to/go/sdk. This inconvenience is caused by a bug in Go SDK 1.10. This bug has been fixed in Go SDK 1.11.

Currently (Go SDK 1.11), the godoc command doesn't support showing documentations of packages outside of the paths specified in the GOPATH environment variable.

The godoc command tries to list the documentations of all the packages under the paths specified in the GOPATH environment variable. If you only want to view the documentations of the standard packages, you can set the GOPATH environment variable to a non-exist path before running godoc, e. g. GOPATH=nonexist godoc -http=:9999.