# Установка пакетов

Был такой эксперимент — [dev](https://golang.github.io/dep/), но он был закопан в пользу механизма модулей — [go mod](https://go.dev/ref/mod).

## Modules, packages and versions

A module is a collection of packages that are released, versioned, and distributed together. Modules may be downloaded directly from version control repositories or from module proxy servers. 

A module is identified by a [module path](https://go.dev/ref/mod#glos-module-path), which is declared in a [`go.mod` file](https://go.dev/ref/mod#go-mod-file), together with information about the module’s dependencies. The module root directory is the directory that contains the `go.mod` file. The main module is the module containing the directory where the `go` command is invoked.

Each package within a module is a collection of source files in the same directory that are compiled together. A package path is the module path joined with the subdirectory containing the package (relative to the module root). For example, the module `"golang.org/x/net"` contains a package in the directory `"html"`. That package’s path is `"golang.org/x/net/html"`.

## go.work

Определяет рабочую область — набор go модулей (по умолчанию, текущая директория — активная рабочая область)

Для работы с workspace  используем команды:

```
go work init
go work use
go work edit
```

Или `golang.org/x/mod/modfile` для выполнения подобных изменений программно.

## Build commands

All commands that load information about packages are module-aware. This includes:

* `go build`
* `go fix`
* `go generate`
* `go get`
* `go install`
* `go list`
* `go run`
* `go test`
* `go vet`

These commands accept the following flags, common to all module commands.

* The `-mod` flag controls whether `go.mod` may be automatically updated and whether the `vendor` directory is used.
  * `-mod=mod` tells the `go` command to ignore the vendor directory and to [automatically update](https://go.dev/ref/mod#go-mod-file-updates) `go.mod`, for example, when an imported package is not provided by any known module.
  * `-mod=readonly` tells the `go` command to ignore the `vendor` directory and to report an error if `go.mod` needs to be updated.
  * `-mod=vendor` tells the `go` command to use the `vendor` directory. In this mode, the `go` command will not use the network or the module cache.
  * By default, if the [`go` version](https://go.dev/ref/mod#go-mod-file-go) in `go.mod` is `1.14` or higher and a `vendor` directory is present, the `go` command acts as if `-mod=vendor` were used. Otherwise, the `go` command acts as if `-mod=readonly` were used.
* The `-modcacherw` flag instructs the `go` command to create new directories in the module cache with read-write permissions instead of making them read-only. When this flag is used consistently (typically by setting `GOFLAGS=-modcacherw` in the environment or by running `go env -w GOFLAGS=-modcacherw`), the module cache may be deleted with commands like `rm -r` without changing permissions first. The [`go clean -modcache`](https://go.dev/ref/mod#go-clean-modcache) command may be used to delete the module cache, whether or not `-modcacherw` was used.
* The `-modfile=file.mod` flag instructs the `go` command to read (and possibly write) an alternate file instead of `go.mod` in the module root directory. The file’s name must end with `.mod`. A file named `go.mod` must still be present in order to determine the module root directory, but it is not accessed. When `-modfile` is specified, an alternate `go.sum` file is also used: its path is derived from the `-modfile` flag by trimming the `.mod` extension and appending `.sum`.

## Vendoring

По умолчанию, модули грузятся в кэш, но если мы хотим поработать со старыми пакетами, мы можем зафризить в папку vendor определенные версии пакетов:

```
go mod vendor
```

Это создаст папку vendor и туда скопирует все пакеты для разработки и тестов. Так же будет создан файл `vendor/modules.txt`, который будет содержать версии пакетов. Можем их посмотреть:

```
go list -m
go version -m
```

Эти команды сравнят версии в vendor с версиями в go.mod. Если они совпадут, вылетит ошибка. Надо будет ввести `go mod vendor` снова.

Начиная с Go 1.14, поддержка vendor включена по умолчанию. Это значит, что `go build` и `go test` будут подгружать модули из vendor, а не идти в интернет или локальный кэш пакетов. go-команды игнорируют любые другие директории vendor, кроме той, что в корневом модуле.

## go get

Обновление модулей в go.mod.

## go install

Установка модулей

## go mod download

Загрузка модуля в кэш модулей

## go list -m

## go mod edit

Редактирование и форматирование go.mod.

## go mod graph

Граф зависимостей

## go mod init

Инициализация модуля в директории

## go mod tidy

## go mod vendor

Подтягивание в папку vendor зависимостей для сборки и теста проекта

## go mod verify

Проверка, что все зависимости разрешены

##


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://appsecurity.gitbook.io/devops/ppc/ppc-langs/backend/go/packages/install-packages.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.