go-getter is a library for Go (golang) for downloading files or directories from various sources using a URL as the primary form of input.
The power of this library is being flexible in being able to download from a number of different sources (file paths, Git, HTTP, Mercurial, etc.) using a single string as input. This removes the burden of knowing how to download from a variety of sources from the implementer.
The concept of a detector automatically turns invalid URLs into proper URLs. For example: "github.com/hashicorp/go-getter" would turn into a Git URL. Or "./foo" would turn into a file URL. These are extensible.
This library is used by Terraform for downloading modules, Otto for dependencies and Appfile imports, and Nomad for downloading binaries.
Package documentation can be found on GoDoc.
Installation can be done with a normal go get:
$ go get github.com/hashicorp/go-getter