[Inori]

Packages and Libraries in Go look scary at first - when I first saw examples, I was kind of freaking out at how complex they looked, but I was looking at the full, built package that was installed via the "go get" command. Anyway, on with the tut.

Installing/Importing/Running Packages and Libraries

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Go doesn't have an official site for package management (like PyPI, RubyGems, or npm), which has both drawbacks and advantages. Expanding on this, there's no metrics for package downloads, but there's also no repository list.

Installing Go packages is easy. After you find a repo for a Go package or library you want to install, simply run the following.

Code:

go get github.com/user/repo

This obviously works for any git repo, but I'd recommend sticking with GitHub, BitBucket, and Launchpad.

If the package has an executable, it will be generated in $GOPATH/bin/, where $GOPATH is the environment variable that the user has to set to install packages. Given this, to run executable, add $GOPATH/bin/ to your PATH variable.

If the package is a library, you would import it as below:

Code:

// regular sub-package import import "math/big" // 3rd party import import "source/user/repo" // example import "github.com/Inori-Y/library"

Updating packages is also easy. Just use the command below.

Code:

go get -u source/user/repo

Making packages

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If you look over any single-file, executable Go code, you'll see the "package main" declaration on the first line. "main" denotes that the file is, well, the main project file, so Go makes it runnable.

For any other packages, you need to create a subdirectory (following convention, with the name of the package) and replace "main" with the package name for any files inside.

If there are multiple files within a package, they automatically share functions and global variables, so if you needed a lookup table, like this, you don't need to import the file like you would in Python or NodeJS.

Exporting Functions

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Function Exports are short and sweet, like most things in Go. Below is a quick comparison of public/protected/private variables in Java vs. Go.

Spoiler: Java

Code:

public class Example{ // public variable, accessible by any class public int pubInt=10; // protected variable, accessible to current package protected int protInt=10; int defaultInt=10; // private variable, accessible by this class private int privInt=10; }

Spoiler: Go

Code:

package example // equivalent to protected and default var protInt int=10 // equivalent to public var PubInt int=10

It's a subtle difference, but any variable or function with an uppercase first letter is accessible to any other package.

As a sidenote, package names are always lower case.

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For a full example of Go's package structure, check out my repo.

This was a bit of a quick one, and it took a while, since I'm doing all my culminating projects and studying for exams. Not sure what I'm going to do for the next tutorial, but I'll try to get it out faster.