Using Go 1.12.12 Toolset

Red Hat Developer Tools 1

Installing and using the Go 1.12.12 toolset

Olga Tikhomirova

otikhomi@redhat.com>

Supriya Takkhi

Peter Macko

Kevin Owen

Vladimir Slavik

Red Hat Developer Group Documentation Team devtools-docs@redhat.com

Legal Notice

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 the Go toolset

The 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.

The 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 the Go toolset:

Table 1.1. Go 1.12.12 Components

Name	Version	Description
golang	1.12.12	A Go compiler.

1.2. Compatibility

The 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 the Go toolset on Red Hat Enterprise Linux 7

The Go toolset is an offering that is distributed as a part of the Red Hat Developer Tools content set, which is available to customers with deployments of Red Hat Enterprise Linux 7. To install the Go toolset, enable the Red Hat Developer Tools and Red Hat Software Collections repositories by using the Red Hat Subscription Management and add the Red Hat Developer Tools GPG key to your system.

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).
Note
We recommend developers to use Red Hat Enterprise Linux Server for access to the widest range of development tools.
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).

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

After the subscription is attached to the system, and the repositories are enabled, you can install the Go toolset as described in Section 1.4, “Installing the 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.
For detailed instructions on subscription to Red Hat Software Collections, see the Red Hat Developer Toolset User Guide, Section 1.4. Getting Access to Red Hat Developer Toolset.

1.4. Installing the Go toolset

The 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 the 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 the Go toolset, see Section 1.3, “Getting access to the Go toolset on Red Hat Enterprise Linux 7”.

Important

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

Install all the components included in the Go toolset for your operating system:
- On Red Hat Enterprise Linux 7, install the go-toolset-1.12.12 package:
```
# yum install go-toolset-1.12
```
- 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.
Create the Go language workspace directory and environment variable:
```
$ 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.
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 the Go and all its features is beyond the scope of this book. For more information, see the resources listed below.

Online Documentation

The Go programming language Documentation — Official documentation for the Go programming language, tools, and libraries.

Chapter 2. go

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

The Go toolset is distributed with go 1.12.12.

2.1. Installing go

In the Go toolset on Red Hat Enterprise Linux 7, go is provided by the go-toolset-1.12.12-golang package and is automatically installed with the go-toolset-1.12.12 package. On Red Hat Enterprise Linux 8, go is provided by the go-toolset module. See Section 1.4, “Installing the Go toolset”.

2.2. Writing Go 1.12.12 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 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:

For Red Hat Enterprise Linux 7:

$ scl enable go-toolset-1.12.12 '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 that 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. This allows you to run a shell session with Go go directly available:

$ scl enable go-toolset-1.12.12 '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-1.12.12 '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.

2.4. 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

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.

2.5. 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:

For Red Hat Enterprise Linux 7:

$ scl enable go-toolset-1.12.12 '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.

2.6. 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-1.12.12 '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-1.12.12 'go help importpath'

For Red Hat Enterprise Linux 8:
```
$ 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:
- For Red Hat Enterprise Linux 7:
```
$ scl enable go-toolset-1.12.12 'go help'
```
- For Red Hat Enterprise Linux 8:
```
$ go help
```
The Go compiler doc command shows documentation for packages. To show documentation for package package_name:
- For Red Hat Enterprise Linux 7:
```
$ scl enable go-toolset-1.12.12 'go doc package_name'
```
  To learn more about the doc command:
```
$ scl enable go-toolset-1.12.12 '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.

Chapter 3. gofmt

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

The Go toolset is distributed with gofmt 1.12.12.

3.1. Installing gofmt

In the Go toolset, gofmt is provided by the go-toolset-1.12.12-golang package and is automatically installed with the go-toolset-1.12.12 package. See Section 1.4, “Installing the Go toolset”.

3.2. 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-1.12.12 '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-1.12.12 'gofmt -l -w -s code_path'

For Red Hat Enterprise Linux 8:
```
$ gofmt -l -w -s code_path
```

3.3. 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-1.12.12 '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.

3.4. 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-1.12.12 '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.

3.5. 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-1.12.12 '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-1.12.12 '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 3.6, “Additional Resources”.

3.6. 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

Command gofmt — Official documentation of the gofmt tool.

Chapter 4. Go Race Detector

The Go toolset includes the Go race detector. The race detector 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

Note

Red Hat Enterprise Linux 8 go-toolset module contains Go race detector. If you are on Red Hat Enterprise Linux 8, skip this step.

In the Go toolset, the race detector is provided by the go-toolset-1.12.12-golang-race package. To install the race detector:

# yum install go-toolset-1.12.12-golang-race

This command installs a variant of the Go standard library with the 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-1.12.12 '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.

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

Data Race Detector — Official documentation of the Go race detector.

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:

Component	Version	Package
`Go`	1.12	go-toolset-1.12.z

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

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

Two RHEL 8 container images provide the same content.

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

The 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:

OpenShift Container Platform 4.2 Image Creation Guide, OpenShift Container Platform-specific guidelines
Using Red Hat Software Collections Container Images, Chapter 2. Using Source-to-Image (S2I).

5.4. Additional Resources

Go 1.12 container images - entries in the Red Hat Container Catalog
Using Red Hat Software Collections Container Images

Chapter 6. Changes in the Go 1.12.12 toolset

This chapter lists some notable changes in the Go 1.12.12 toolset since its previous release.

6.1. Go

Go has been updated from version 1.11.5 to 1.12.12.

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Using Go 1.12.12 Toolset

Installing and using the Go 1.12.12 toolset

Olga Tikhomirova

Supriya Takkhi

Peter Macko

Kevin Owen

Vladimir Slavik

Chapter 1. Go

1.1. About the Go toolset

1.2. Compatibility

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

Additional Resources

1.4. Installing the Go toolset

Additional Resources

1.5. Additional Resources

Online Documentation

Chapter 2. go

2.1. Installing go

2.2. Writing Go 1.12.12 programs

Additional Resources

2.3. Using the go compiler

2.4. Running a Go Program

2.5. Installing Go projects

2.6. Downloading Go projects

2.7. Additional Resources

Installed documentation

Online Documentation

See Also

Chapter 3. gofmt

3.1. Installing gofmt

3.2. Formatting code

3.3. Previewing changes to code

3.4. Simplifying code

3.5. Refactoring code

3.6. Additional Resources

Online documentation

See also

Chapter 4. Go Race Detector

4.1. Installing the Race Detector

See also

4.2. Using the Race Detector

4.3. Additional Resources

Online documentation

See also

Chapter 5. Container images with Go Toolset

5.1. Images contents

5.2. Accessing the images

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

5.4. Additional Resources

Chapter 6. Changes in the Go 1.12.12 toolset

6.1. Go

Legal Notice