File I/O

This section discusses file I/O in Go, which includes the use of the io.Reader and io.Writer interfaces, buffered and unbuffered I/O, as well as the bufio package.

The io/ioutil package (https://pkg.go.dev/io/ioutil) has been deprecated since Go version 1.16. Existing Go code that uses the functionality of io/ioutil will continue to work, but it is better to stop using that package.

The io.Reader and io.Writer interfaces

This subsection presents the definitions of the popular io.Reader and io.Writer interfaces because these two interfaces are the basis of file I/O in Go—the former allows you to read from a file, whereas the latter allows you to write to a file. The definition of the io.Reader interface is the following:

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

This definition, which should be revisited when we want one of our data types to satisfy the io.Reader interface, tells us the following:

• The Reader interface...