Git – Go, go get, go install, local packages, and version control

gitgopackage

I am having trouble understanding the workflow for creating a go project that has local packages.

Say I create a new project, using git for version control, which has a main.go file and a tools.go file which will be in package utils. So I have a directory structure such as this:

/myproject/
   main.go
   utils/
     tools.go

main.go looks like this:

package main
import "./utils"
func main() {
    utils.DoSomthing()
}

and tools.go looks like this:

package utils;
func DoSomething() {
}

Everything works just fine locally, using go build and go run. But this is being hosted on github, and I'd like to be able to have others use the go get command to install it. So the local package import must be changed to use the format "github.com/user/project/utils", which works, except now I have two copies of the source code, and the real problem is that the copy with the git history has an import that makes use of the downloaded copy. So if I'm working on the copy with the git history, any changes made to tools.go will go unnoticed, because it will be using the downloaded copy.

So I'm wondering if someone can explain the right way of using go get, version control, and package imports within the same project.

Best Answer

I've just written a short step-by-step guide on how I am using the new go tool and github.com. You might find it useful:

1. Setup your GOPATH

You can set the environment variable GOPATH to any directory you like. If you have larger projects, it's probably a good idea to create a different GOPATH for each of them. I would recommend this approach especially for the deployment, so that updating a library for project A doesn't break project B which might require an earlier version of the very same library.

Also note that you can set your GOPATH to a list of directories, delimited by colons. So you might have a GOPATH containing all commonly used packages, and separate GOPATHS for each project with additonal packages or different versions of existing packages.

But unless your are working on a lot of different Go projects simultaneously, its probably enough to have just a single GOPATH locally. So, let's create one:

mkdir $HOME/gopath

Then you need to set two environment variables to tell the go tool where it can find existing Go packages and where it should install new ones. It's probably best to add the following two lines to your ~/.bashrc or ~/.profile (and do not forget to reload your .bashrc afterwards).

export GOPATH="$HOME/gopath"
export PATH="$GOPATH/bin:$PATH"

2. Create a new project

If you want to create a new Go project which should be hosted at github.com later, you should create this project under $GOPATH/src/github.com/myname/myproject. It's important that the path matches the URL of the github.com repo, because the go tool will follow the same convention. So, let's create the project root and initialize a new git repository there:

mkdir -p $GOPATH/src/github.com/myname/myproject
cd $GOPATH/src/github.com/myname/myproject
git init

Because I do not like to type such long paths, I normally create symbolic links for the projects I am currently working on in my home folder:

ln -s $GOPATH/src/github.com/myname/myproject ~/myproject

3. Write your application

Start coding and don't forget to git add and git commit your files. Also, do not use relative imports like import "./utils" for sub-packages. They are currently undocumented and shouldn't be used at all, because they won't work with the go tool. Use imports like github.com/myname/myproject/utils instead.

4. Publish your project

Create a new repository at github.com, upload your SSH public key if you haven't done that before and push your changes to the remote repository:

git remote add origin git@github.com:myname/myproject.git
git push origin master

5. Continue working on your project

If you have set the GOPATH in your .bashrc and if you have created a symlink to your project in your home folder, you can just type cd myproject/ and edit some files there. Afterwards, you can commit the changes using git commit -a and send them to github.com by doing a git push.

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