Simple example of packages and imports in golang

This is day 7 out of 100 days of golang coding.

By requests of my friends this post is about packages, files and imports.

Packages in go is the same as modules and libraries in other languages. To make a package you need two decide two things: package path and package name.

In my example package name is helloworld and because it is day7 it is inside day7 folder. Full path looks like: github.com/vorozhko/go-tutor/day7/helloworld.
Full path is calculated based on $GOPATH variable which is ~/go by default, but can be set to any other in .bashrc file.

All files with the same package name will belong to one package and will share private and public variable like it is one single file. To make variable or function public it’s name must start with capital letter. Lets see an example:

hello.go

 

world.go

Function ‘say’ and constant  ‘prefix’ only visible inside package helloworld.
Function SayName will be visible outside of the package.

You can import new package from any place in your workspace using following code:

main.go

To import a package you have to use full path to the package relatively to your $GOPATH folder.
From here we can call helloworld.SayName, because it is visible outside of the package.

To manage imports in your go files it is recommended to use goimports tool. It will automatically insert package declaration in import as necessary. It also supported by many code editors.

 

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