Go tools are awesome

Yes, they are. And that’s why I love Go. Almost all important tools come together with Go installation, but there are also some you can install additionally depends on your needs: golint, errcheck, etc.

Let’s start with standard Go tools.

go get

The most common way to install a Go package is to use a go get. If you need fixed versions you may use dep for dependencies management. go get downloads the packages named by the import paths, along with their dependencies. It then installs the named packages, like go install.

go get github.com/golang/lint/golint

There are some helpful flags:

• -u forces the tool to sync with the latest version of the repo.
• -d if you just want to clone a repo to your GOPATH and skip the building and installation phase.

go build / go install

These 2 commands compile packages and dependencies. Both go install and go build will compile the package in the current directory when ran without additional arguments. If the package is package main, go build will place the resulting executable in the current directory. go install will put it in $GOPATH/bin (using the first element of $GOPATH if you have more than one). Additionally go install will install compiled dependencies in $GOPATH/pkg. To achieve the same effect with go build, use go build -i. If the package is not package main, go install will compile the package and install it in $GOPATH/pkg.

The go build command lets you build an executable file for any Go-supported target platform, on your platform. This means you can test, release and distribute your application without building those executables on the target platforms you wish to use.

GOOS=windows GOARCH=amd64 go build github.com/mholt/caddy/caddy

If you are curious about the Go toolchain, or using a cross-C compiler and wondering about flags passed to the external compiler, or suspicious about a linker bug, use -x to see all the invocations.

go build -x
WORK=/var/folders/2g/_fnx086940v6k_yt88fdtqw80000gn/T/go-build614085896
mkdir -p $WORK/github.com/plutov/go-snake-telnet/_obj/
mkdir -p $WORK/github.com/plutov/go-snake-telnet/_obj/exe/
...

I often use -ldflags option when build Go programs:

• To optimize Go Binary Size.
• To set variable value during the build.

go build -ldflags="-X main.Version 1.0.0"

go build -gcflags used to pass flags to the Go compiler. go tool compile -help lists all the flags that can be passed to the compiler.

go test

This command has a lot of options, but the ones I use often are:

• -race to run Go race detector.
• -run to filter tests to run by regex and the -run flag: go test -run=FunctionName.
• -bench to run benchmarks.
• -cpuprofile cpu.out writes a CPU profile to the specified file before exiting.
• -memprofile mem.out writes a memory profile to the file after all tests have passed.
• I always use -v. It prints the test name, its status (failed or passed), how much it took to run the test, any logs from the test case, etc.
• -cover measures the percentage of lines of code that are executed while running a suite of tests.

go list

It lists the packages named by the import paths, one per line.

go env

Prints Go environment information:

go env
GOARCH="amd64"
GOBIN="/Users/pltvs/go/bin"
...

go fmt

Most used tool for me, because I run it on file save. It will reformat your code based on Go’s standards.

There is also goimports based on gofmt which updates your Go import lines, adding missing ones and removing unreferenced ones.

go vet

I also run it on save, go vet examines Go source code and reports suspicious constructs, such as Printf calls whose arguments do not align with the format string.

go generate

The go generate command was added in Go 1.4, “to automate the running of tools to generate source code before compilation.”

The Go tool scans the files relevant to the current package for lines with a “magic comment” of the form //go:generate command arguments. This command does not have to do anything related to Go or code generation. For example:

package project

//go:generate echo Hello, Go Generate!

func Add(x, y int) int {
	return x + y
}

$ go generate
Hello, Go Generate!

Tools for reading code

We spend more time reading code than writing it, and as such, tooling that helps us reading code is an important addition to the tool box of any good gopher.

go doc / godoc

This sounds quite similar to javadoc and other similar tools, but Go documentation does not have any extra formatting rules. Everything is plain text.

For instance, we can get information about json.Encoder by running:

go doc json.Encoder
package json // import "encoding/json"

type Encoder struct {
        // Has unexported fields.
}
...

If go doc is able to give us information about any identifier in our GOPATH, godoc is able to provide full documentation for packages in text form:

godoc errors
use 'godoc cmd/errors' for documentation on the errors command

PACKAGE DOCUMENTATION

package errors
...

Non standard go tools

Let’s see what tools community created to make Gophers happy.

golint

I also run it on file save.

go get -u github.com/golang/lint/golint

errcheck

go get github.com/kisielk/errcheck

This tool detects when an error is silently ignored. This means that for a function that returns at least one error we are omitting to check the returned values.

Given a foo() error function, we’ll say that:

• foo() is silently omitting the error, while
• _ = foo() is omitting the error explicitly.

P.S.

Go community is very active and always creating new useful tools, please leave a comment if you know some other tools you find useful.