Go makes it easy to create a zip of your app that runs across Linux, without dependencies. However, end user discovery and update management remain a challenge. Snaps fill this gap, letting you distribute a Go app in an app store experience for end users.
Installing Go applications often consists of downloading pre-built binaries (or running
go get). When distributed this way, getting updates is an exercise left to the reader. With snapcraft it’s just one command to produce a bundle that works anywhere and can be automatically updated.
Here are some snap advantages that will benefit many Go projects:
snap install mygoapp, regardless of distribution.
Ready to get started? By the end of this guide, you’ll understand how to make a snap of your Go app that can be published in the Snap Store, showcasing it to millions of Linux users.
For a brief overview of the snap creation process, including how to install snapcraft and how it’s used, see Snapcraft overview. For a more comprehensive breakdown of the steps involved, take a look at Creating a snap.
Snaps are defined in a single YAML file placed in the root folder of your project. The following example shows the entire snapcraft.yaml file for an existing project, HTTPLab. Don’t worry, we’ll break this down.
name: test-httplab version: git summary: An interactive web server. description: | HTTPLab let you inspect HTTP requests and forge responses. confinement: devmode base: core18 parts: test-httplab: plugin: go go-importpath: github.com/gchaincl/httplab source: . source-type: git build-packages: - gcc apps: test-httplab: command: bin/httplab
snapcraft.yaml file starts with a small amount of human-readable metadata, which usually can be lifted from the GitHub description or project README.md. This data is used in the presentation of your app in the Snap Store.
name: test-httplab version: git summary: An interactive web server. description: | HTTPLab let you inspect HTTP requests and forge responses.
name must be unique in the Snap Store. Valid snap names consist of lower-case alphanumeric characters and hyphens. They cannot be all numbers and they also cannot start or end with a hyphen.
git for the version, the current git tag or commit will be used as the version string. Versions carry no semantic meaning in snaps.
summary can not exceed 79 characters. You can use a chevron ‘>’ in the
description key to declare a multi-line description.
The base keyword declares which base snap to use with your project. A base snap is a special kind of snap that provides a run-time environment alongside a minimal set of libraries that are common to most applications:
See Base snaps for more details.
The next section describes the level of confinement applied to your app.
Snaps are containerised to ensure more predictable application behaviour and greater security. Unlike other container systems, the shape of this confinement can be changed through a set of interfaces. These are declarations that tell the system to give permission for a specific task, such as accessing a webcam or binding to a network port.
It’s best to start a snap with the confinement in warning mode, rather than strictly applied. This is indicated through the
devmode keyword. When a snap is in devmode, runtime confinement violations will be allowed but reported. These can be reviewed by running
Because devmode is only intended for development, snaps must be set to strict confinement before they can be published as “stable” in the Snap Store. Once an app is working well in devmode, you can review confinement violations, add appropriate interfaces, and switch to strict confinement.
Parts define what sources are needed to assemble your app. Parts can be anything: programs, libraries, or other needed assets.
In this case we have one: the httplab source code. In other cases, these can point to local directories, remote git repositories, or tarballs.
The Go plugin will build using the version of Go on the system running snapcraft.
When using local sources, snapcraft needs to construct a suitable
GOPATH. For this it uses
go-importpath to know where the sources should live within
parts: test-httplab: plugin: go go-importpath: github.com/gchaincl/httplab source: . source-type: git build-packages: - gcc
For more details on Go-specific metadata, see The go plugin.
Apps are the commands and services exposed to end users. If your command name matches the snap
name, users will be able run the command directly. If the names differ, then apps are prefixed with the snap
httplab.command-name, for example). This is to avoid conflicting with apps defined by other installed snaps.
If you don’t want your command prefixed you can request an alias for it on the Snapcraft forum. These are set up automatically when your snap is installed from the Snap Store.
apps: test-httplab: command: bin/httplab
If your application is intended to run as a service you simply add the line
daemon: simple after the command keyword. This will automatically keep the service running on install, update, and reboot.
You can download the example repository with the following command:
$ git clone https://github.com/snapcraft-docs/httplab
After you’ve created the snapcraft.yaml, you can build the snap by simply executing the snapcraft command in the project directory:
$ snapcraft Using 'snapcraft.yaml': Project assets will be searched for from the 'snap' directory. Launching a VM. [...] Snapped test-httplab_v0.0.1+git74.a92fbb7-dirty_amd64.snap
The resulting snap can be installed locally. This requires the
--dangerous flag because the snap is not signed by the Snap Store. The
--devmode flag acknowledges that you are installing an unconfined application:
$ sudo snap install test-httplab_*.snap --devmode --dangerous
You can then try it out:
$ test-httplab -h
Removing the snap is simple too:
$ sudo snap remove test-httplab
To share your snaps you need to publish them in the Snap Store. First, create an account on the dashboard. Here you can customise how your snaps are presented, review your uploads and control publishing.
You’ll need to choose a unique “developer namespace” as part of the account creation process. This name will be visible by users and associated with your published snaps.
Make sure the
snapcraft command is authenticated using the email address attached to your Snap Store account:
$ snapcraft login
You can publish your own version of a snap, provided you do so under a name you have rights to. You can register a name on dashboard.snapcraft.io, or by running the following command:
$ snapcraft register mygosnap
Be sure to update the
name: in your
snapcraft.yaml to match this registered name, then run
Use snapcraft to push the snap to the Snap Store.
$ snapcraft upload --release=edge mygosnap_*.snap
If you’re happy with the result, you can commit the snapcraft.yaml to your GitHub repo and turn on automatic builds so any further commits automatically get released to edge, without requiring you to manually build locally.
Congratulations! You’ve just built and published your first Go snap. For a more in-depth overview of the snap building process, see Creating a snap.
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