Learning Go, 2nd Edition

Chapter 13. The Standard Library

One of the best parts of developing with Go is being able to take advantage of its standard library. Like Python, it has a “batteries included” philosophy, providing many of the tools that you need to build an application. Since Go is a relatively new language, it ships with a library that is focused on problems faced in modern programming environments.

I can’t cover all the standard library packages, and luckily, I don’t have to, as there are many excellent sources of information on the standard library, starting with the documentation. Instead, I’ll focus on several of the most important packages and how their design and use demonstrate the principles of idiomatic Go. Some packages (errors, sync, context, testing, reflect, and unsafe) are covered in their own chapters. In this chapter, you’ll look at Go’s built-in support for I/O, time, JSON, and HTTP.

io and Friends

For a program to be useful, it needs to read in and write out data. The heart of Go’s input/output philosophy can be found in the io package. In particular, two interfaces defined in this package are probably the second and third most-used interfaces in Go: io.Reader and io.Writer.

Note

What’s number one? That’d be error, which you already looked at in Chapter 9.

Both io.Reader and io.Writer define a single method:

type Reader interface {
    Read(p []byte) (n int, err error)
}

type Writer interface {
    Write(p []byte) (n int, err error)
}

The Write method on the io.Writer interface ...