Add Go guidelines to developer docs

doc/development/README.md

@@ -123,3 +123,7 @@ description: 'Learn how to contribute to GitLab.'
 ## Compliance
 
 - [Licensing](licensing.md) for ensuring license compliance
+
+## Go guides
+
+- [Go Guidelines](go_guide/index.md)

doc/development/contributing/style_guides.md

@@ -21,6 +21,7 @@
    of _prohibited this user from being saved due to the following errors:_ the
    text should be _sorry, we could not create your account because:_
 1. Code should be written in [US English][us-english]
+1. [Go](../go_guide/index.md)
 
 This is also the style used by linting tools such as
 [RuboCop](https://github.com/bbatsov/rubocop) and [Hound CI](https://houndci.com).

doc/development/go_guide/index.md

+# Go standards and style guidelines
+
+This document describes various guidelines and best practices for GitLab
+projects using the [Go language](https://golang.org).
+
+## Overview
+
+GitLab is built on top of [Ruby on Rails](https://rubyonrails.org/), but we're
+also using Go for projects where it makes sense. Go is a very powerful
+language, with many advantages, and is best suited for projects with a lot of
+IO (disk/network access), HTTP requests, parallel processing, etc. Since we
+have both Ruby on Rails and Go at GitLab, we should evaluate carefully which of
+the two is best for the job.
+
+This page aims to define and organize our Go guidelines, based on our various
+experiences. Several projects were started with different standards and they
+can still have specifics. They will be described in their respective
+`README.md` or `PROCESS.md` files.
+
+## Code Review
+
+We follow the common principles of
+[Go Code Review Comments](https://github.com/golang/go/wiki/CodeReviewComments).
+
+Reviewers and maintainers should pay attention to:
+
+- `defer` functions: ensure the presence when needed, and after `err` check.
+- Inject dependencies as parameters.
+- Void structs when marshalling to JSON (generates `null` instead of `[]`).
+
+### Security
+
+Security is our top priority at GitLab. During code reviews, we must take care
+of possible security breaches in our code:
+
+- XSS when using text/template
+- CSRF Protection using Gorilla
+- Use a Go version without known vulnerabilities
+- Don't leak secret tokens
+- SQL injections
+
+Remember to run
+[SAST](https://docs.gitlab.com/ee/user/project/merge_requests/sast.html)
+**[ULTIMATE]** on your project (or at least the [gosec
+analyzer](https://gitlab.com/gitlab-org/security-products/analyzers/gosec)),
+and to follow our [Security
+requirements](../code_review.md#security-requirements).
+
+Web servers can take advantages of middlewares like [Secure](https://github.com/unrolled/secure).
+
+### Finding a reviewer
+
+Many of our projects are too small to have full-time maintainers. That's why we
+have a shared pool of Go reviewers at GitLab. To find a reviewer, use the
+[Engineering Projects](https://about.gitlab.com/handbook/engineering/projects/)
+page in the handbook. "GitLab Community Edition (CE)" and "GitLab Community
+Edition (EE)" both have a "Go" section with its list of reviewers.
+
+To add yourself to this list, add the following to your profile in the
+[team.yml](https://gitlab.com/gitlab-com/www-gitlab-com/blob/master/data/team.yml)
+file and ask your manager to review and merge.
+
+```yaml
+projects:
+  gitlab-ee: reviewer go
+  gitlab-ce: reviewer go
+```
+
+## Code style and format
+
+- Avoid global variables, even in packages. By doing so you will introduce side
+  effects if the package is included multiple times.
+- Use `go fmt` before committing ([Gofmt](https://golang.org/cmd/gofmt/) is a
+  tool that automatically formats Go source code).
+
+### Automatic linting
+
+All Go projects should include these GitLab CI/CD jobs:
+
+```yaml
+go lint:
+  image: golang:1.11
+  script:
+    - go get -u golang.org/x/lint/golint
+    - golint -set_exit_status
+```
+
+Once [recursive includes](https://gitlab.com/gitlab-org/gitlab-ce/issues/56836)
+become available, you will be able to share job templates like this
+[analyzer](https://gitlab.com/gitlab-org/security-products/ci-templates/raw/master/includes-dev/analyzer.yml).
+
+## Dependencies
+
+Dependencies should be kept to the minimum. The introduction of a new
+dependency should be argued in the merge request, as per our [Approval
+Guidelines](../code_review.html#approval-guidelines). Both [License
+Management](https://docs.gitlab.com/ee/user/project/merge_requests/license_management.html)
+**[ULTIMATE]** and [Dependency
+Scanning](https://docs.gitlab.com/ee/user/project/merge_requests/dependency_scanning.html)
+**[ULTIMATE]** should be activated on all projects to ensure new dependencies
+security status and license compatibility.
+
+### Modules
+
+Since Go 1.11, a standard dependency system is available behind the name [Go
+Modules](https://github.com/golang/go/wiki/Modules). It provides a way to
+define and lock dependencies for reproducible builds. It should be used
+whenever possible.
+
+There was a [bug on modules
+checksums](https://github.com/golang/go/issues/29278) in Go < v1.11.4, so make
+sure to use at least this version to avoid `checksum mismatch` errors.
+
+### ORM
+
+We don't use object-relational mapping libraries (ORMs) at GitLab (except
+[ActiveRecord](https://guides.rubyonrails.org/active_record_basics.html) in
+Ruby on Rails). Projects can be structured with services to avoid them.
+[PQ](https://github.com/lib/pq) should be enough to interact with PostgreSQL
+databases.
+
+### Migrations
+
+In the rare event of managing a hosted database, it's necessary to use a
+migration system like ActiveRecord is providing. A simple library like
+[Journey](https://github.com/db-journey/journey), designed to be used in
+`postgres` containers, can be deployed as long-running pods. New versions will
+deploy a new pod, migrating the data automatically.
+
+## Testing
+
+We should not use any specific library or framework for testing, as the
+[standard library](https://golang.org/pkg/) provides already everything to get
+started. For example, some external dependencies might be worth considering in
+case we decide to use a specific library or framework:
+
+- [Testify](https://github.com/stretchr/testify)
+- [httpexpect](https://github.com/gavv/httpexpect)
+
+Use [subtests](https://blog.golang.org/subtests) whenever possible to improve
+code readability and test output.
+
+### Benchmarks
+
+Programs handling a lot of IO or complex operations should always include
+[benchmarks](https://golang.org/pkg/testing/#hdr-Benchmarks), to ensure
+performance consistency over time.
+
+## CLIs
+
+Every Go program is launched from the command line.
+[cli](https://github.com/urfave/cli) is a convenient package to create command
+line apps. It should be used whether the project is a daemon or a simple cli
+tool. Flags can be mapped to [environment
+variables](https://github.com/urfave/cli#values-from-the-environment) directly,
+which documents and centralizes at the same time all the possible command line
+interactions with the program. Don't use `os.GetEnv`, it hides variables deep
+in the code.
+
+## Daemons
+
+### Logging
+
+The usage of a logging library is strongly recommended for daemons. Even though
+there is a `log` package in the standard library, we generally use
+[logrus](https://github.com/sirupsen/logrus). Its plugin ("hooks") system
+makes it a powerful logging library, with the ability to add notifiers and
+formatters at the logger level directly.
+
+### Tracing and Correlation
+
+[LabKit](https://gitlab.com/gitlab-org/labkit) is a place to keep common
+libraries for Go services. Currently it's vendored into two projects:
+Workhorse and Gitaly, and it exports two main (but related) pieces of
+functionality:
+
+- [`gitlab.com/gitlab-org/labkit/correlation`](https://gitlab.com/gitlab-org/labkit/tree/master/correlation):
+  for propagating and extracting correlation ids between services.
+- [`gitlab.com/gitlab-org/labkit/tracing`](https://gitlab.com/gitlab-org/labkit/tree/master/tracing):
+  for instrumenting Go libraries for distributed tracing.
+
+This gives us a thin abstraction over underlying implementations that is
+consistent across Workhorse, Gitaly, and, in future, other Go servers. For
+example, in the case of `gitlab.com/gitlab-org/labkit/tracing` we can switch
+from using Opentracing directly to using Zipkin or Gokit's own tracing wrapper
+without changes to the application code, while still keeping the same
+consistent configuration mechanism (i.e. the `GITLAB_TRACING` environment
+variable).
+
+### Context
+
+Since daemons are long-running applications, they should have mechanisms to
+manage cancellations, and avoid unnecessary resources consumption (which could
+lead to DDOS vulnerabilities). [Go
+Context](https://github.com/golang/go/wiki/CodeReviewComments#contexts) should
+be used in functions that can block and passed as the first parameter.
+
+## Dockerfiles
+
+Every project should have a `Dockerfile` at the root of their repository, to
+build and run the project. Since Go program are static binaries, they should
+not require any external dependency, and shells in the final image are useless.
+We encourage [Multistage
+builds](https://docs.docker.com/develop/develop-images/multistage-build/):
+
+- They let the user build the project with the right Go version and
+  dependencies.
+- They generate a small, self-contained image, derived from `Scratch`.
+
+Generated docker images should have the program at their `Entrypoint` to create
+portable commands. That way, anyone can run the image, and without parameters
+it will display its help message (if `cli` has been used).
+
+---
+
+[Return to Development documentation](../README.md).