为什么许多golang项目直接从GitHub导入？

Question

I'm totally new to golang, and am wondering, why many golang projects write in their source code like this way:

import  "github.com/stretchr/testify/assert"

What if this testify moved to bitbucket?

Why not download testify and import testify, like other languages?

Answer 1

Before I answer your question, you need to understand about the way golang manages it's packages and dependencies.

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To download packages, use the go get command. Usage example:

$ go get github.com/stretchr/testify

Above command will downloads the testify package then store it locally under work space with structure following it's url (TL;DR work space path is registered as $GOPATH env variable).

$GOPATH/src/github.com/stretchr/testify

An explanation from the doc why the downloaded package name will follow it's url:

Get downloads the packages named by the import paths, along with their dependencies.

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Now about your question:

Why does many golang project directly import from GitHub?

The statement import "github.com/stretchr/testify/assert" doesn't mean that the package is directly imported from github website (through http). It's imported from your local, from github.com/stretchr/testify path under $GOPATH/src. The package was downloaded and stored there before, so it can be imported into any project.

Below is an explanation from the documentation about the import statements:

The Go path ($GOPATH) is used to resolve import statements.

Also take a look at some code below (taken from my local).

$ echo $GOPATH
/Users/novalagung/Documents/go

$ go get -u github.com/stretchr/testify
# package will be downloaded into $GOPATH/src folder using the same structure as the github url

$ tree -L 1 $GOPATH/src/github.com/stretchr/testify
/Users/novalagung/Documents/go/src/github.com/stretchr/testify
├── Gopkg.lock
├── Gopkg.toml
├── LICENSE
├── README.md
├── _codegen
├── assert
├── doc.go
├── http
├── mock
├── package_test.go
├── require
├── suite
└── vendor

So if you want to import any packages, it must be under $GOPATH/src folder.

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what if this testify moved to bitbucket?

It has no effect on your local project, because the required package already downloaded before. However, if you want to update it, you might need to change the package path to follows it's new url, maybe like bitbucket.org/stretchr/testify/assert? depends on what the new bitbucket url looks like.

But I don't think the owner of the testify will do that, since it'll break lot people of codes.