The document discusses the history and evolution of dependency management in Go, including early approaches using $GOPATH and tools like godep, as well as more recent solutions like vendoring dependencies in a vendor folder to avoid conflicts between different dependency versions, with tools like dep and glide supporting this approach and an experimental vgo tool proposing integration of vendoring into the core Go tooling.

1. Go West
Vendoring
Gothenburg’s Golang meetup!

2. Topics
● A bit of background
● File structure, $GOPATH
● Dependencies
● Conflicts
● Vendoring
● The future

3. Background
2009 - only a compiler and linker with makefiles, no packages
2010 - `goinstall`, current package structure
2011 - `go` command, with `go get` (v1 of Golang)
2013 - `godep`, deps stored in project, edits $GOPATH
2014 - `glide`, deps in vendor folder understood by `go`
2016 - `dep`, improved usability and flexibility

4. File structure, $GOPATH
$GOPATH - i.e. ~/go `go get
github.com/maxekman/project`
bin/ - compiled binaries
pkg/ - compiled static libraries
src/ - sources, structure from the import URL
github.com/
maxekman/
project/

5. Dependencies
Package files in `$GOPATH/src/github.com/maxekman/project/a.go`
Defined with `package project` as first lines in `a.go`
Imported with `import “github.com/maxekman/project”`
Used as `project.Function()`
The `package <name>` statement defines the package name
Not the package folder name

6. Conflicts
Package A in `src/A` needs D from `src/D`
Package B in `src/B` also needs D from `src/D`
However B needs a later version of D with a new package API
Impossible to solve using $GOPATH
Can maybe be solved by using a project based $GOPATH
Similar to virtualenvs in Python, very messy!

7. Vendoring
Dependencies stored in a folder called `vendor/`
Looks like a mini version of the `$GOPATH/src` folder
Understood by `go build` and `go run` to find packages
Can’t use `go get` to save in vendor folder
Both `dep` and `glide` uses vendoring

8. The future
Integration in the `go` tool
`vgo` - versioned/vendored golang experiment
Wraps the `go` tool, but adds support for versioning
Adds the concept of a module, a close group of packages
Version in import statement: `import “pkg” v1.0.0`
Blog posts by Russ Cox: https://research.swtch.com/vgo