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So we're coming along on our tour of the go language.



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We know how to use variables.



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We know how to make decisions with an if statement or a switch statement.



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We've had a look at pointers.



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We've had a look at interfaces, custom data types, maps, slices.



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And it's time to look at another important concept known as packages.



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And if you've worked in any other programming language, you're familiar with use of packages.



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Java uses them and calls them packages, imports, things.



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And we've been using packages right along.



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Whether you're aware of whether you're aware of it or not, I have an empty mango here.



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And if I try to print to the log log print line, hello, it actually imports a package for me.



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And in Goaland, if I roll over it, it'll tell me what the package is called, log and how to use it,



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import log and then describe it.



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Well, we can also create our own packages log as part of the standard library.



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We don't have to import it or we don't have to define it.



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It's already defined for us, but we can actually define our own and we do that in a really simple way.



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I'm going to show you how to do this again in a later lecture, but it's good to get our feet wet right



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now.



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We need to tell our Idy and go that we're using packages or go module's go module's is the way we use



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packages.



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Now, he used to be you'd have to define a gopalnath environment variable and put things in certain



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folders and it was a real pain.



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It's much easier now.



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So I'm going to open my terminal and type go mode in it and then I'm going to give my the package I'm



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working on, which is my program.



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Aname.



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Conventionally you start you name things by prefixing it with the name of the git repository where it's



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going to live.



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You can call it whatever you want, but it's useful even if you don't push to GitHub or BitBucket or



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any repository to use this naming convention because you might push at some point GitHub dot com.



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My username is Chiseller and I'll aim this package, my nice program.



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So it created it.



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Now, when it does that, it creates a go mod file and the mod file is automatically created by that



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command we just typed, and inside of it it tells me what version of go I'm using one point one five.



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You might be a later version, but it doesn't matter.



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And it names this module, whatever I've just named it.



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And there's another thing that I sometimes have to fight with goaland to get it.



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Recognizing it, you go to goaland preferences if you're in goal end and search for goal modules so



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you can type modules up here and modules and it will show it.



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And there it is.



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And make sure that you have this checked enable go modules and apply and then click, OK, and there's



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probably similar steps to follow in visual studio code, but maybe Visual Studio Code is smart enough



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to do it without being kicked three or four times, which apparently goaland wants and requires.



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Once I've done that, I can start creating my own packages and I do that by going to my root level of



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the directory, creating a new directory, the root level of my project, creating a new directory.



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I'm going to call my helpers and it creates a folder and inside of that will create a go file, which



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I will call helper Stocco.



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And Goaland opened it for me automatically and you'll see that it names this package.



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Whatever the name of this directory is, it happens to be called helper's.



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And I can do things like define a type type some type which will just be a struct and it'll have two



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fields, one for type name, which is a string and one for type number which is in it.



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And I'm actually using these, I'm just creating a type that I can use in my main goal.



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So back in my main go file, I can actually use that type.



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How do I do that via my var?



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I'm just naming a variable and it's a type, some type and it automatically shows me that helper's some



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type is available and when I choose that it imports it and it imports it.



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Using the package name.



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I specified what I wrote Gomaa in it and then it names that package.



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Which one of you important.



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I can create another package by creating another directory.



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I haven't done anything with my var but the fact is I've imported it so I can do things like my dot



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type name is equal to some name and then print out to the log logged print line my va dot type name.



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And if I run this go run mango it will work and there it is printed out.



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So that's what packages are.



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And the thing is you don't just define types in packages.



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I can also in my helper defined functions that I can call by importing the helpers package and then



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I have access to everything in that package and that's all there is to it.



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So packages are incredibly useful, incredibly powerful, a nice way of getting our code organized into



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logical groupings and will be using those regularly as time goes on.



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So you're going to go through the same exercise in the next section when we start actually building



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things.



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But it's important to have at least some concept of what a package is right now.