Go Modules.

Writing Go Modules is as simple as writing code in a file inside a folder. The folder is known as the module.

• A module is a folder

• There could be more than one .go files in the module with module declaration at top package gomodule

• Any function from any of the .go file inside a module can be called from any other file in the same module.

• File names does not matter inside a module as far as importing a module is concerned.

• While importing a module, the whole of the module is imported. That means all the .go files in that module is available, to call their functions from. The functions are called with the module name, not the file name.

• While declaring a module the .mod file holds the key. It declares the URL and module name as module saumya.learning/gomodule. The respective .go files in that module, must declare the package declaration as package gomodule and the URL must be a live URL.

Example of a module declaration in a .mod file

module saumya.learning/gomodule

The .go files in that module must declare the package declaration as below.

package gomodule

Just remember that these declarations are must be the first line in the respective files.

The URL in the module declaration saumya.learning/gomodule must be a valid URL. Because while importing the module in another module, the Go is going to import the module from that URL. In this example, the URL is saumya.learning which must exist in the internet.

Well, there is a way to work with local modules. That is, importing modules from local file system. It has to be specifically declared in the .mod file as below.

replace saumya.learning/gomodule => ../2_ago

In this example, it is importing a Go Module from a folder, relative to our working folder.

The mod Command

Creation of a Go module is done with mod command.

go mod init saumya.learning/hello

Here it is creating a .mod file with module declaration as module saumya.learning/hello.

Happy Going.