Using Go Toolset

Go Toolset is a Red Hat offering for developers on the Red Hat Enterprise Linux platform, available as a Technology Preview. 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.

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

Go Toolset is available for Red Hat Enterprise Linux versions 7.3 and 7.4 on the following architectures:

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. In order to install 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 key to your system.

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

Additional Resources

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 in order to install Go Toolset on your system. For detailed instructions on how to associate your system with an appropriate subscription and get access to Go Toolset, see Section 1.3, “Getting Access to Go Toolset”.

Additional Resources

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

Online Documentation

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”.

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.

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

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

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)

}

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

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'

$ 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'

$ scl enable go-toolset-7 'bash'

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

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

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

$ ./file_name

./hello

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

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'

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

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

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'

$ 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'

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

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

Online Documentation

See Also

In Go Toolset, gofmt 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”.

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

scl enable go-toolset-7 'gofmt -w code_path'

$ scl enable go-toolset-7 'gofmt -w code_path'

This command will directly change 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:

scl enable go-toolset-7 'go fmt -l -w -s code_path'

$ scl enable go-toolset-7 'go fmt -l -w -s code_path'

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

scl enable go-toolset-7 'gofmt -d code_path'

$ scl enable go-toolset-7 '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.

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

scl enable go-toolset-7 'gofmt -s code_path'

$ scl enable go-toolset-7 '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.

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:

scl enable go-toolset-7 'gofmt -r rewrite_rule code_path'

$ scl enable go-toolset-7 '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:

scl enable go-toolset-7 'gofmt -r rewrite_rule -d code_path'

$ scl enable go-toolset-7 '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”.

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

In Go Toolset, the race detector is provided by the go-toolset-7-golang-race package. To install the race detector:

yum install go-toolset-7-golang-race

# yum install go-toolset-7-golang-race

A variant of the Go standard library with the runtime race detection enabled is installed.

See Also

To use the runtime race detector for 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:

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

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

When you run the resulting executable, the race detector will print warnings to the standard output when a race is detected.

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

The devtools/go-toolset-7-rhel7 image provides content corresponding to the following packages:

To pull the devtools/go-toolset-7-rhel7 image, run the following command as root:

docker pull registry.access.redhat.com/devtools/go-toolset-7-rhel7

# docker pull registry.access.redhat.com/devtools/go-toolset-7-rhel7

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

To do so, set the following build environment variables:

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-7-rhel7 md2man-app

$ 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-7-rhel7 md2man-app

To fully leverage the Go Toolset 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 Toolset usage with Source-to-Image is beyond the scope of this book. For more information about Source-to-Image, refer to the OpenShift Container Platform 3.7 Image Creation Guide, Chapter 4. S2I Requirements and Using Red Hat Software Collections Container Images, Chapter 2. Using Source-to-Image (S2I).

Go has been updated from version 1.8.3 to 1.8.7. This release also fixes the discovered security issues like CVE-2018-6574, CVE-2017-15041, and CVE-2017-15042.

Additionally, the following bugs have been fixed:

Notable changes include: