We won’t be writing any code in this chapter; instead, we’ll explore an API using the methods mentioned previously. To do so, we’ll need to have Postman and curl installed. We’ll also need to create a free account in Postman so that we can use the application to its fullest potential.

OpenAPI is a standard from the OpenAPI Initiative that describes HTTP APIs and is the de facto standard for REST APIs.

It imparts a detailed description of all the URLs, methods, parameters, resources, entities, and serialization mechanisms available while also providing examples of how to use the API in code.

In this section, we’ll explore the basic shape of OpenAPI and the main things you need to look at to understand an API. However, we won’t get into the details of the OpenAPI format. Instead, I’ll help you understand an API through its OpenAPI documentation.

We’ll explore how to document APIs using OpenAPI in Chapter 11.

For now, let’s talk more about the OpenAPI file and its format.

The OpenAPI file

The OpenAPI file is a YAML Ain’t Markup Language (YAML) file containing general API information and a list of paths. Each path represents a URL in your API; you can have a set of accepted methods for that URL...

Postman is an HTTP client specially designed to consume APIs. It’s the de facto standard in the industry to explore and try APIs with a graphical interface. It’s compatible with OpenAPI and allows us to explore APIs but also interact with them directly there.

In this section, we’re going to explore the basic usage of Postman and give you a sneak peek at its potential. We’ll start by importing an API definition, studying it, and interacting with it by sending a request.

So, let’s start by installing the tool and importing an API.

Importing an API

You can download and install Postman locally from https://www.postman.com/downloads/ or directly from their web page at https://web.postman.co. It works perfectly fine in both cases, but you should consider using the installable application for local development.

One of the fantastic things about Postman is that it comes with many already existing APIs that are easy to incorporate...

curl is the Swiss Army knife of REST API testing. It can build any request you need with the headers and parameters you want, all in a compact and easy-to-use CLI. If you don’t have it installed on your system, you can use your system package manager or follow the instructions at https://curl.se/.

If you’re like me and prefer to interact with the command line, you’ll love curl (and you probably already know it). Not only that, but curl is used everywhere and is supported by a lot of applications, so it isn’t rare to have curl command-line examples in API documentation that provide support for extracting curl calls from places such as the Web Developers Tools of Firefox and Chrome in the Network tab, allowing you to reproduce network calls in your command line by copy and pasting.

In this section, we’ll explore using the curl command to send requests and get information such as headers in the response.

Getting information

The...

In this chapter, we explored different ways to understand APIs better. First, we looked at using OpenAPI to get information on what we can do and how to use an API. We can explore APIs in read-only and “map” fashion using the YAML format or the OpenAPI-generated documentation pages. We saw how powerful and valuable this can be by looking at some examples and details about various parameters and methods.

Then, we considered another option – not only for exploring but also for interacting with APIs quickly and powerfully: Postman. We learned how to explore and interact with well-known public APIs or build our own and test them through the Postman interface.

Finally, we explored curl, a great CLI tool that provides us with everything we need to interact with our APIs from the command line and helps us with testing and debugging.

But this has nothing to do with Go, which is what this book is about. So, let’s jump into the next chapter and...