Visibility is the attribute of a function or a variable to be visible to different parts of the program. So a variable can be used only in the function that is declared, in the entire package or in the entire program.
How can I set the visibility of a variable or function? Well, it can be confusing at the beginning but it cannot be simpler:
Uppercase definitions are public (visible in the entire program).
Lowercase are private (not seen at the package level) and function definitions (variables within functions) are visible just in the scope of the function.
Here you can see an example of a public function:
package hello
func Hello_world(){
println("Hello World!")
}
Here, Hello_world is a global function (a function that is visible across the entire source code and to third party users of your code). So, if our package is called hello, we could call this function from outside of this package by using hello.Hello_world() method.
package different_package
import "github.com/sayden/go-design-patters/first_chapter/hello"
func myLibraryFunc() {
hello.Hello_world()
}
As you can see, we are in the different_package package. We have to import the package we want to use with the keyword import. The route then is the path within your $GOPATH/src that contains the package we are looking for. This path conveniently matches the URL of a GitHub account or any other Concurrent Versions System(CVS) repository.