module.exports = router;

The line "module.exports = router;" in the Go programming language is used to export a router object from a module.

Here is an explanation of each step:

1. "module" refers to the module object in Go. A module is a collection of related Go files that can be imported and used by other programs.

2. "exports" is a property of the module object that allows specific objects or functions to be made available to other modules.

3. "=" is the assignment operator, used to assign a value to a variable or property.

4. "router" is the name of the object being exported. In this case, it refers to a router object, which is commonly used in web development to handle HTTP requests and route them to the appropriate handler functions.

5. The entire line "module.exports = router;" is a statement that exports the router object from the module, making it available for other modules to import and use.

This line of code is typically found at the end of a module file, indicating that the router object is the main object being exported from that module. Other modules can then import this module and access the router object for their own purposes.