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Chapter 2. go

go is a build tool and dependency manager for the Go programming language.

Go Toolset is distributed with go 1.8.7.

Important

Go Toolset and go are available as a Technology Preview. See the Technology Preview Features Support Scope for more details.

Libraries used by go in Go Toolset provide no ABI compatibility with past or future releases.

Customers deploying Go Toolset are encouraged to provide feedback to Red Hat.

2.1. Installing go

In Go Toolset, go is provided by the go-toolset-7-golang package and is automatically installed with the go-toolset-7 package. See Section 1.4, “Installing Go Toolset”.

2.2. Writing Go Programs

When creating a Go program, developers must follow the rules for Go workspace layout. The .go source files must be placed in subdirectory of $GOPATH/src.

Example 2.1. Creating a Go Program

Consider a program named hello consisting of a single source file named hello.go: 

$ mkdir -p $GOPATH/src/hello
$ cd $GOPATH/src/hello
$ touch hello.go

Edit the file hello.go in your favorite text editor to add the following text: 

package main

import (
    "fmt"
    "net/http"
)

func Welcome(w http.ResponseWriter, req *http.Request) {

    fmt.Fprintf(w, "<h1>Welcome to the Go toolset.</h1>")

}

func main() {

    fmt.Println("Hello.")
    fmt.Println("Starting http server.")
    // Register handler function
    http.HandleFunc("/welcome", Welcome)
    fmt.Println("Go to localhost:8080/welcome")
    fmt.Println("To terminate press CTRL+C.")
    // Start server
    http.ListenAndServe(":8080", nil)

}

Additional Resources

  • Workspaces — Description of the Go language workspace organization. Official documentation for the Go programming language.

2.3. Using the go Compiler

To build a Go program using the command line, change to the project directory and run the go compiler as follows: 

$ scl enable go-toolset-7 'go build -o output_file go_main_package'

This creates a binary file named output_file in the current working directory. If the -o option is omitted, the compiler creates a file named after the go_main_package, go_main_package.

If go_main_package is not a main package or if multiple projects or *.go files are specified, the resulting binaries are discarded. In that case, the go build command is used to verify that the supplied projects or files can be built.

Note that you can execute any command using the scl utility, causing it to be run with the Go Toolset binaries available. This allows you to run a shell session with Go Toolset go directly available: 

$ scl enable go-toolset-7 'bash'

Example 2.2. Compiling a Go Program Using the Command Line

Assuming that you have successfully created the program hello as shown in Example 2.1, “Creating a Go Program”, compile the program: 

$ scl enable go-toolset-7 'go build hello.go'

This creates a new binary file called hello in the current working directory.

2.4. Running a Go Program

When go compiles a program, it creates an executable binary file. To run this program on the command line, change to the directory with the executable file and run the program: 

$ ./file_name

Example 2.3. Running a Go Program on the Command Line

Assuming that you have successfully compiled the hello binary file as shown in Example 2.2, “Compiling a Go Program Using the Command Line”, run it by typing the following at a shell prompt: 

$ ./hello
Hello.
Starting http server.
Go to localhost:8080/welcome
To terminate press CTRL+C.

2.5. Installing Go Projects

Installing a Go project means that its executable files and libraries are compiled, and copied to appropriate directories in the Go Workspace. The go tool can then use the executable files and libraries in further projects. Dependencies of the installed project are installed, too.

To install a Go project, run the go tool: 

$ scl enable go-toolset-7 'go install go_project'

The install command accepts the same options as the build command.

2.6. Downloading Go Projects

To download a 3rd party Go project from an online source and install it, run the go tool: 

$ scl enable go-toolset-7 'go get 3rd_party_go_project'

For more details about the possible values of 3rd_party_go_project option, run the following command: 

$ scl enable go-toolset-7 'go help importpath'

2.7. Additional Resources

A detailed description of the go compiler and its features is beyond the scope of this book. For more information, see the resources listed below.

Installed Documentation

  • The Go compiler help command provides information on its usage. To show the help index: 

    $ scl enable go-toolset-7 'go help'

  • The Go compiler doc command shows documentation for packages. To show documentation for package package_name: 

    $ scl enable go-toolset-7 'go doc package_name'

    To learn more about the doc command: 

    $ scl enable go-toolset-7 'go help doc'

Online Documentation

  • Command go — Official documentation of the go compiler.

See Also