Using Go 1.13 Toolset

Red Hat Developer Tools 1

Installing and using Go 1.13 Toolset

Eva-Lotte Gebhardt

Zuzana Zoubkova

Olga Tikhomirova

Supriya Takkhi

Peter Macko

Kevin Owen

Vladimir Slavik

Red Hat Developer Group Documentation Team

Abstract

Go is a Red Hat offering for developers on the Red Hat Enterprise Linux platform. The Using Go provides an overview of this product, explains how to invoke and use the Go versions of the tools, and links to resources with more in-depth information.

Chapter 1. Go

1.1. About Go Toolset

Go Toolset is a Red Hat offering for developers on the Red Hat Enterprise Linux platform. It provides the Go programming language tools and libraries. Go is alternatively known as golang.

Go Toolset is distributed as a part of Red Hat Developer Tools for Red Hat Enterprise Linux 7 and is available as a module in Red Hat Enterprise Linux 8.

The following components are available as a part of Go Toolset:

Table 1.1. Go 1.13 components

NameVersionDescription

golang

1.13

A Go compiler.

1.2. Compatibility

Go Toolset is available for Red Hat Enterprise Linux 7 and Red Hat Enterprise Linux 8 on the following architectures:

  • The 64-bit Intel and AMD architectures
  • The 64-bit ARM architecture
  • The IBM Power Systems architecture
  • The little-endian variant of IBM Power Systems architecture
  • The IBM Z Systems architecture

1.3. Getting access to Go Toolset on Red Hat Enterprise Linux 7

This chapter lists the steps to perform before installing Go Toolset on a Red Hat Enterprise Linux 7 system. Complete the following steps to attach a subscription that provides access to the repository for Red Hat Developer Tools, and then enable the Red Hat Developer Tools and Red Hat Software Collections repositories.

Prerequisites

  • Verify that wget is installed on your system. The tool is available from the default Red Hat Enterprise Linux repositories. To install it, run the following command as root:

    # yum install wget

Procedure

  1. Get the latest subscription data from the server:

    # subscription-manager refresh
  2. Use the following command to register the system:

    # subscription-manager register

    You can also register the system by following the appropriate steps in Registering and Unregistering a System in the Red Hat Subscription Management document.

  3. Display a list of all subscriptions that are available for your system and identify the pool ID for the subscription:

    # subscription-manager list --available

    This command displays the subscription name, unique identifier, expiration date, and other details related to it. The pool ID is listed on a line beginning with Pool ID.

  4. Attach the subscription that provides access to the Red Hat Developer Tools repository. Use the pool ID you identified in the previous step.

    # subscription-manager attach --pool=<appropriate pool ID from the subscription>
  5. Verify the list of subscriptions attached to your system:

    # sudo subscription-manager list --consumed
  6. Enable the rhel-7-variant-devtools-rpms repository:

    # subscription-manager repos --enable rhel-7-variant-devtools-rpms

    Replace variant with the Red Hat Enterprise Linux system variant (server or workstation).

    Consider using Red Hat Enterprise Linux Server to access the widest range of the development tools.

  7. Enable the rhel-variant-rhscl-7-rpms repository:

    # subscription-manager repos --enable rhel-variant-rhscl-7-rpms

    Replace variant with the Red Hat Enterprise Linux system variant (server or workstation).

  8. Add the Red Hat Developer Tools key to your system:

    # cd /etc/pki/rpm-gpg
    # wget -O RPM-GPG-KEY-redhat-devel https://www.redhat.com/security/data/a5787476.txt
    # rpm --import RPM-GPG-KEY-redhat-devel

Once the subscription is attached to the system and the repositories are enabled, install Go Toolset as described in Section 1.4, “Installing Go Toolset”.

Additional Resources

  • For more information on how to register your system using Red Hat Subscription Management and associate it with subscriptions, see the Red Hat Subscription Management collection of guides.

1.4. Installing Go Toolset

Go Toolset is distributed as a collection of RPM packages that can be installed, updated, uninstalled, and inspected by using the standard package management tools that are included in Red Hat Enterprise Linux. Note that a valid subscription that provides access to the Red Hat Developer Tools content set is required to install Go Toolset on a Red Hat Enterprise Linux 7 system. For detailed instructions on how to associate your Red Hat Enterprise Linux 7 system with an appropriate subscription and get access to Go Toolset, see Section 1.3, “Getting access to Go Toolset on Red Hat Enterprise Linux 7”.

Important

Before installing Go Toolset, install all available Red Hat Enterprise Linux updates.

  1. Install all the components included in Go Toolset for your operating system:

    • On Red Hat Enterprise Linux 7, install the go-toolset-1.13 package:

      # yum install go-toolset-1.13
    • On Red Hat Enterprise Linux 8, install the go-toolset module:

      # yum module install go-toolset

      This installs all development and debugging tools, and other dependent packages to the system.

  2. Choose a Go language workspace directory and save its location as an environment variable to the $HOME/.bashrc file:

    $ mkdir -p workspace_dir
    $ echo 'export GOPATH=workspace_dir' >> $HOME/.bashrc
    $ source $HOME/.bashrc

    Select an appropriate value for the workspace_dir directory. A common choice is $HOME/go.

    Use the -p flag with the mkdir command to create the workspace_dir directory along with the directories that lead to it.

    If the GOPATH variable is not set, the go compiler uses the ~/go directory.

Additional resources

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

1.5. Additional resources

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

Online documentation

Chapter 2. go

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

Go Toolset is distributed with go 1.13.

2.1. Writing Go 1.13 programs

When creating a Go program, developers must follow the rules for Go workspace layout. The .go source files must be placed in the 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 a text editor of your choice, 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 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.

2.2. 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:

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'go build -o output_file go_main_package'
  • For Red Hat Enterprise Linux 8:

    $ 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

You can execute any command using the scl utility on Red Hat Enterprise Linux 7, causing it to be run with the Go binaries available. To use Go Toolset on Red Hat Enterprise Linux 7 without a need to use scl enable with every command, run a shell session with:

$ scl enable go-toolset-1.13 'bash'

Example 2.2. Compiling a Go program using the command line

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

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'go build hello.go'
  • For Red Hat Enterprise Linux 8:

    $ go build hello.go

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

2.3. 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

After 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.

2.4. Installing compiled 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. It is thus appended to your working project and does not form a separate structure, rendering all Go projects cohesive systems.

To install a Go project, run the go tool:

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'go install go_project'
  • For Red Hat Enterprise Linux 8:

    $ go install go_project

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

2.5. Downloading Go projects

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

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'go get 3rd_party_go_project'
  • For Red Hat Enterprise Linux 8:

    $ go get 3rd_party_go_project

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

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'go help importpath'
  • For Red Hat Enterprise Linux 8:

    $ go help importpath

2.6. 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:

    • For Red Hat Enterprise Linux 7:

      $ scl enable go-toolset-1.13 'go help'
    • For Red Hat Enterprise Linux 8:

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

    • For Red Hat Enterprise Linux 7:

      $ scl enable go-toolset-1.13 'go doc package_name'

      To learn more about the doc command:

      $ scl enable go-toolset-1.13 'go help doc'
    • For Red Hat Enterprise Linux 8:

      $ go doc package_name

      To learn more about the doc command:

      $ go help doc

Online documentation

  • Command go — Official documentation of the go compiler.

See also

  • Chapter 1, Go — An overview of Go and more information on how to install it on your system.

Chapter 3. gofmt

gofmt is a code formatting tool for the Go programming language, packaged together with the go compiler.

Go Toolset is distributed with gofmt 1.13.

3.1. Formatting code

To format all code in the code_path path, run the gofmt tool as follows:

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'gofmt -w code_path'
  • For Red Hat Enterprise Linux 8:

    $ gofmt -w code_path

This command directly changes the code in the code_path path. When code_path is a single file, the changes apply only to the file. When code_path is a directory, all .go files in the directory are processed.

When the code_path is omitted, gofmt reads standard input instead.

To print the formatted code to standard output instead of writing to the original file, omit the -w option.

It is possible to invoke gofmt through the go compiler with the fmt command. To achieve the same results as the command above, run:

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'gofmt -l -w -s code_path'
  • For Red Hat Enterprise Linux 8:

    $ gofmt -l -w -s code_path

3.2. Previewing changes to code

To preview changes done by formatting code in a given path code_path, run the gofmt tool with the -d option as follows:

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'gofmt -d code_path'
  • For Red Hat Enterprise Linux 8:

    $ gofmt -d code_path

The output in unified diff format is printed to standard output.

It is possible to combine both the -d and -w options.

3.3. Simplifying code

To simplify code in a given path code_path, run the gofmt tool with the -s option as follows:

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'gofmt -s code_path'
  • For Red Hat Enterprise Linux 8:

    $ gofmt -s code_path

The code under code_path is simplified. Use the -d option to show the differences, and use the -w option to apply the changes to the code.

3.4. Refactoring code

The gofmt tool can be used to refactor code by applying arbitrary substitutions. To refactor code in a given path code_path according to a rule rewrite_rule, run the gofmt tool with the -r option as follows:

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'gofmt -r rewrite_rule code_path'
  • For Red Hat Enterprise Linux 8:

    $ gofmt -r rewrite_rule code_path

The code under code_path is refactored according to the rule rewrite_rule. Use the -d option to show the differences, and use the -w option to apply the changes to the code. The additional options must be placed after the rule rewrite_rule:

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'gofmt -r rewrite_rule -d code_path'
  • For Red Hat Enterprise Linux 8:

    $ gofmt -r rewrite_rule -d code_path

Detailed description of the rewrite rules is beyond the scope of this book. For more information, see the resources listed in Section 3.5, “Additional resources”.

3.5. Additional resources

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

Online documentation

See also

  • Chapter 1, Go — An overview of Go Toolset and more information on how to install it on your system.

Chapter 4. Go race detector

Go Toolset includes the Go race detector, which is a feature of the Go standard library. The race detector must be enabled at compile time and is used at runtime.

4.1. Installing the race detector

On Red Hat Enterprise Linux 7, the race detector is provided by the go-toolset-1.13-golang-race package:

# yum install go-toolset-1.13-golang-race

On Red Hat Enterprise Linux 8 it is provided by the golang-race package:

# yum install golang-race

This command installs a variant of the Go standard library that contains runtime race detection.

4.2. Using the race detector

To use the runtime race detector in a Go project, add the -race option to the go tool commands used when manipulating the project.

For a minimal approach to using the race detector, build the project with the -race option:

  • For Red Hat Enterprise Linux 7:

    $ scl enable go-toolset-1.13 'go build -race -o output_file go_main_package'
  • For Red Hat Enterprise Linux 8:

    $ go build -race -o output_file go_main_package

Run the resulting executable binary file, and the race detector prints warnings to the standard output when a race is detected.

Important

The race detector has a significant runtime resource overhead.

Note

You can execute any command using the scl utility on Red Hat Enterprise Linux 7, causing it to be run with the Go binaries available. To use Go Toolset on Red Hat Enterprise Linux 7 without a need to use scl enable with every command, run a shell session with:

$ scl enable go-toolset-1.13 'bash'

4.3. Additional resources

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

Online documentation

See also

  • Chapter 1, Go — An overview of Go and more information on how to install it on your system.

Chapter 5. Container images with Go Toolset

Go Toolset is available as container images for RHEL 7 and RHEL 8. They can be downloaded from the Red Hat Container Registry.

5.1. Images contents

The RHEL 7 and RHEL 8 container images provide content corresponding to the following packages:

ComponentVersionPackage

Go

1.13

go-toolset-1.13

5.2. Accessing the images

To pull the required image, run the following command as root:

  • For the RHEL 7 container images:
# podman pull registry.redhat.io/devtools/go-toolset-rhel7
# podman pull registry.redhat.io/ubi7/go-toolset
Note

The two RHEL 7 container images provide the same content.

  • For the RHEL 8 container images:
# podman pull registry.redhat.io/rhel8/go-toolset
# podman pull registry.redhat.io/ubi8/go-toolset
Note

The two RHEL 8 container images provide the same content.

5.3. Using as builder images with Source-to-Image

Go Toolset container image is prepared for use as a Source-to-Image (S2I) builder image.

To do so, set the following build environment variables:

IMPORT_URL
Set this variable to a URL specifying the location of the code. The rules for the go get command option apply.
INSTALL_URL

Set this variable to a URL specifying the location of the package that will provide the application’s main executable file when built. The rules for the go install command option apply.

This variable can be omitted if the main package location is identical with the location specified by the IMPORT_URL variable.

Example 5.1. Building a Go application image using Source-to-Image

To build the md2man package from its GitHub repository:

$ s2i build -e IMPORT_URL='github.com/cpuguy83/go-md2man' -e INSTALL_URL='github.com/cpuguy83/go-md2man' git://github.com/cpuguy83/go-md2man  registry.access.redhat.com/devtools/go-toolset-rhel7 md2man-app

A locally available application image md2man-app is built from the repository on GitHub using the go-toolset container image.

To fully leverage the Go as a S2I builder image, build custom images based on it, with modified S2I assemble scripts and further modifications to accomodate the particular application being built.

A detailed description of the Go usage with Source-to-Image is beyond the scope of this document. For more information about Source-to-Image, see:

5.4. Additional resources

Chapter 6. Changes in Go 1.13 Toolset

Go Toolset has been updated from version 1.12 to 1.13. Notable changes include:

  • Go can now use a FIPS-certified cryptographic module when the RHEL system is booted in the FIPS mode. Users can enable this mode manually using the GOLANG_FIPS=1 environment variable.
  • The Delve debugger, version 1.3.2, is now available for Go. It is a source-level debugger for the Go (golang) programming language. Currently, Delve is supported only on the 64-bit Intel and AMD architectures for both Red Hat Enterprise Linux 7 and Red Hat Enterprise Linux 8.

    To install the Delve debugger:

    On Red Hat Enterprise Linux 7, there is no special action needed. Delve is automatically installed with Go Toolset.

    On Red Hat Enterprise Linux 8, run the following command as root:

    # yum install delve

    To debug a helloworld.go program using Delve:

    On Red Hat Enterprise Linux 7, run the following command:

    $ scl enable go-toolset-1.13 'dlv debug helloworld.go'

    On Red Hat Enterprise Linux 8, run the following command:

    $ dlv debug helloworld.go

    For more information about Delve, see the Delve documentation.

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