Improving the List Output Format

We’ve made good progress on our to-do list tool so far, but the list output is still not very informative.

Powerful interfaces

At this moment, executing the command ./todo -list gives us this output:

Another ToDo item
Improve usage
Improve output

There are various ways of improving the output formatting. For instance, if we don’t own the API code, our only alternative is to format the output in the command-line tool implementation. But we own the API, so we can leverage the powerful interfaces feature of Go to implement the list output formatting in the todo.List type directly. By using this approach, anyone using our API experiences a consistent output format.

An interface in Go implements a contract, but unlike other languages, Go interfaces only define behavior ...