go

Top Reference Material

Here’s the reference material I use to help guide me on basic style, design, and general idiomatic Go practices.

Starter Template

I saved this as a snippet for vscode to get up and running quickly with something better than the defaults for handling func main isolation. I’ve been working on modifying this a bit as I don’t really like using args, but am trying not to overcomplicate things as a new gopher.

I tend to like better flag parsing than using args, but it’s still a better pattern to get functions isolated from main to easily test.

The gist that I’ve taken from this and discussions in the community is ensure that main is where program termination is dedicated instead of handling this in your functions. This isolation of logic from main ensures you can more easily setup your tests as well, since func main() isn’t testable.

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package main

// package template from:
import (
    "errors"
    "fmt"
    "io"
    "os"
)

const (
    // exitFail is the exit code if the program
    // fails.
    exitFail = 1
)

func main() {
    if err := run(os.Args, os.Stdout); err != nil {
        fmt.Fprintf(os.Stderr, "%s\n", err)
        os.Exit(exitFail)
    }
}

func run(args []string, stdout io.Writer) error {
    if len(args) == 0 {
        return errors.New("no arguments")
    }
    for _, value := range args[1:] {
        fmt.Fprintf(stdout, "Running %s", value)
    }
    return nil
}

Using Go for Task Running & Automation

My preferred tool at this time is Mage.

Mage replaces the need for Bash or PowerShell scripts in your repo for core automation tasks, and provides the benefits of Go (cross-platform, error handling paradigm, readability, performance, etc).

Getting Started With Mage

Use Go

• Run go install github.com/magefile/[email protected]
• Run go install github.com/iwittkau/[email protected]
• asdf: asdf plugin-add mage && asdf install mage latest && asdf local mage latest

Intialize a New Project

• Scripts-To-Rule-Them-All-Go : A repo I’ve setup as quick start template for a Mage enabled repository with linting and core structure already in place.
• Magetools : Reusable packages that can be pulled in to jump start common tasks or utilities.
  • Examples:
    • Enhanced go formatter with mage go:wrap.
    • Preinstall common Go tools such as the language server, dlv, gofumpt, golangci-lint, and more with mage go:init.
    • Provide a github repo for a go binary and use in tasks. If the binary isn’t found, it will automatically grab it when invoked.
    • Pre-commit registration and tooling.
    • Install Git Town, Bit, and other cool git helpers with mage gittools:init.
    • Chain together all your core tasks with mage init to allow for a fully automated dev setup.

Why Should I Care About Mage?

• I’ve never felt my automation was as robust, stable, and easy to debug as when I’ve used Mage.
• I’ve done a lot of experimenting with others, and had primarily relied on InvokeBuild (powershell based) in the past.
• Mage takes the prize for ease of use.
• You can migrate a make file relatively easily if you want to just call tools directly.
• You can benefit from using Go packages directly as you up your game.
  • Example: instead of calling kubectl directly, I’ve used a helm Go library that does actions like validation, linting, and templating directly from the same core code that kubectl itself uses.

Mage Basics

• Mage is just Go code.
• It does a little “magic” by simplying matching some functions that match basic signature such as error output, like func RunTests(dir string) error {...}.
• You can get around needing mage by creating Go files, but you’d have to add basic args handling for the main() entry point, and help generation.
• Mage basically tries to simplify the cli invocation by auto-discovering all the matched functions in your magefiles directory and providing as tasks.
• Mage does not currently support flags, though this is actively being looked at.
  • This means you are best served by keeping tasks very very simple. Ie mage deploy project dev is about as complex as I’d recommend.
  • Normally, you’d invoke with mytool -project ProjectName -env dev and positions wouldn’t matter. With mage, it’s positional for simplicity so best to keep simple!

My Mage Tips

• Use the pattern shown in my template repo above.
  • Use magefiles directory.
  • Provide a single magefile.go that does your imports and basic commands. If it’s a big project then just have it import and put all your tasks in subdirectories that it imports.
• Provide a magefiles/constants/constants.go && vars.go rather than being worried about globals. This is for build automation, and having a configured file with standards that shouldn’t change or global variables is a nice alternative to needing more yaml files.
• Use Pterm for enchanced logging experience, provides some beautiful output for users.
• For extra benefit, standardize with a mage doctor command in your project that validates issues experienced and gets added to over time. This can help troubleshooting any environment or project issues if you maintain and add a list of checks being run. Using Pterm you can make this into a nice table output like this:

Testing

• Go test will automatically ignore directories and files starting with . or _, see go command - cmd/go - pkg.go.dev .

Modules

What are Go Modules?

Go Modules are primarily a dependency management solution.

A module:

• Is primarily a dependency management tool, not a project organization tool.
• Is imported to get access to public exported members in your own project.
• One module can have n binaries produced.
• A module can be used in a monorepo or single CLI tool.

A module doesn’t:

• Handle build or binary path metadata.
• Have any relationship to the produced artifacts.

Module Tips

• Use canconical import path (aka) github.com/sheldonhull/mygomod if you want to support go install commands.
• Use mymod.local if no need to support remote imports or installs.
  • This allows gofumpt and tooling to correctly sort the imports from standard library apart from your own imports, without requiring canonical name format.
• Stick with one module in the repo if possible, to simplify tooling, linting, and testing. This is important in monorepos as much of the tooling that uses paths like go test ./... will not work with multi-module repos in a project.

Project & Build Tooling

• Use devtools.go to create a list of cli tools that should be installed with Mage.
• Use tools.go to put _ "remotemodulename" in, and identify clearly that a tool such as Stringer or linters are not dependencies for the primary module, but instead are tooling dependencies.

Pre-Commit

Using Pre-Commit Tooling

Here’s how to setup pre-commit for Go projects.

1. Install pre-commit for macOS: brew install pre-commit or see directions for curl/other options for WSL, Windows, Linux, etc.
2. Use the template from TekWizely/pre-commit-golang: Pre-Commit hooks for Golang with support for Modules
   1. Several options are provided for fmt oriented commands. Comment out any duplicates that don’t apply.
3. Finally initialize the pre-commit hooks in your repo by running: pre-commit install

Validate everything is working by running: pre-commit run --all-files

Periodically, you can run pre-commit autoupdate to ensure the latest version of the pre-commit hooks are upgraded.

Logging

At this stage, I’m using zerolog as I found it very easy to get moving with structured logs.

The output of this demo looks pretty good!

Here’s a functional demo that can be used to bootstrap a new project with this.

Code Coverage Report

original post: ¹

Use gopherbadge²

1

go install github.com/jpoles1/[email protected]

• Set ![gopherbadger-tag-do-not-edit]() in the readme, and then this gets replaced with a code coverage percentage badge.
• Generate the required code coverage reports using:

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go test ./... -coverprofile ./artifacts/cover.out
go tool cover -html=./artifacts/cover.out -o ./artifacts/coverage.html
gopherbadger -md="README.md,coverage.md" -tags 'unit'

VSCode

Custom Tasks

Default Shells

This can ensure default behavior is processed on each OS, customizing the shell to use.

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{
  "version": "2.0.0",
  "presentation": {
    "echo": false,
    "reveal": "always",
    "focus": false,
    "panel": "dedicated",
    "showReuseMessage": true
  },
  "linux": {
    "options": {
      "shell": {
        "executable": "/usr/local/bin/zsh",
        "args": [
          "-l",
          "-c"
        ],
      }
    },
    "type": "shell"
  },
  "windows": {
    "options": {
      "shell": {
        "executable": "pwsh"
      }
    },
    "type": "shell"
  },
  "osx": {
    "options": {
      "shell": {
        "executable": "/usr/local/bin/zsh",
        "args": [
          "-l",
          "-c"
        ]
      }
    },
    "type": "shell"
  },
  "tasks": []
}

Run Lint

Add this to your .vscode/tasks.json file and you’ll get the full linting output in your problems pane.

By default, the golangci-lint config should include --fast to avoid impact to your editing.

This will ensure all tasks that a pre-commit check or CI check will be run and provided in the problems panel.

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"tasks": [
    {
      "label": "go-lint-all",
      "detail": "This runs the full range of checks and the VSCode problem matcher will pull all of them in. Without this, the default behavior of VSCode is to run with --fast to reduce impact to IDE.",
      "type": "shell",
      "command": "golangci-lint",
      "args": [
        "run",
        "--out-format",
        "colored-line-number"
      ],
      "problemMatcher": [
        "$go"
      ],
      "presentation": {
        "echo": true,
        "reveal": "always",
        "focus": true,
        "panel": "dedicated",
        "showReuseMessage": true,
        "clear": true
      }
    },

Run Nicely Formatted Test Output

Tparse

While the testing extension is great, sometimes I just want to see a console summary. This task uses Tparse and provides a nicely formatted summary (including coverage numbers, cached tests, and more).

Install tparse with: go install github.com/mfridman/[email protected].

Run manually like this: GOTESTS='slow' go test ./... -v -cover -json | tparse -all

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{
  "label": "go-test-formatted-output",
  "type": "shell",
  "command": "go",
  "options": {
    "env": {
      "GOTEST": "slow integration",
    }
  },
  "args": [
    "test",
    "./...",
    "-v",
    "-cover",
    "-json",
    "|",
    "tparse",
    "-all"
  ],
  "problemMatcher": []
},

Gotestsum

Install with: go install gotest.tools/[email protected].

Then run like this: gotestsum or try the alternative formats like: gotestsum --format dots-v2 or --format pkgname, or --format testname.

Effective Go

Principles I’ve gleaned over-time and am quoting or bookmarking.

Don’t hide the cost

Source: Bill Kennedy in Ultimate Go ³

If we are doing construction to a variable, we use value construction. Avoid pointer semantic construction if not in the return.

Example:

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// clear visible cost of the allocation by value construction and passing of pointer back up the call stack
func createSomething() *something {
  u := something{
    name: "example",
  }
  return &u // <--- This makes clear the cost and allocation back up the callstack.
}
// cost is obscured by construction being a pointer
// and returning a value that is not clear to reader if value or pointer
func createSomething()*something {
  u := &something{
    name: "example",
  }
  return u // <--- Not good. Hides the cost, and require reading function further to find that this is a pointer.
}

Making cost obvious and visible is a big priority for readable maintainable code with a team.

Running External Commands

Repos