Go Package io

External

• https://golang.org/pkg/io/
• https://golang.org/pkg/io/ioutil/

Internal

• Standard Library
• File Operations in Go

Overview

The io package consists of a few functions, but mostly interfaces used by other packages.

io.EOF

The error returned by I/O operations that encounter the end of file. It can be tested with:

_, err := ...
if errors.Is(err, io.EOF) {
  // is EOF 
  ...
}

Reader

https://golang.org/pkg/io/#Reader

An interface that exposes Read().

Readers can be used to unmarshall JSON into structs as shown here:

Unmarshalling JSON from a Reader into a struct

Files opened with os.Create() implement io.Reader.

Wrapping a []byte into a Reader

A []byte can be wrapped into a Reader with:

import "bytes"

bs := []byte("something")
r := bytes.NewReader(bs)

Getting a Reader from a string

s := "some string"
reader := strings.NewReader(s)

Writer

https://golang.org/pkg/io/#Writer

Files opened with os.Create() implement io.Writer.

Closer

https://golang.org/pkg/io/#Closer

Files opened with os.Create() implement io.Closer.

ReadCloser

An interface that exposes basic Read() and Close() methods. The http.Request body is a ReadCloser. See Reader.