Basic calculator CLI using Cobra and Viper

Let us pull some of the pieces together and create a separate and simple CLI using the Cobra CLI framework and Viper for configuration. A simple idea that we can easily implement is a basic calculator that can add, subtract, multiply, and divide values. The code for this demo exists within the Chapter-4-Demo repository for you to follow along.

The Cobra CLI commands

The commands are created with the following cobra-cli command calls:

cobra-cli add add
cobra-cli add subtract
cobra-cli add multiply
cobra-cli add divide

Calling these commands successfully generates the code for each command, ready for us to fill in the details. Let us show each command and how they each are similar and different.

The add command

The add command, addCmd, is defined as a pointer to the cobra.Command type. Here, we set the fields for the command:

// addCmd represents the add command
var addCmd = &cobra.Command{
    Use...