Readers/writers

Remember, Go uses a structural type system. This makes any data type that implements Read([]byte) (int,error) an io.Reader, and any data type that implements Write([]byte) (int,error) an io.Writer. There are many uses of this property in the standard library. In this recipe, we will look at some of the common uses of readers and writers.

Reading data from a reader

An io.Reader fills a byte slice you pass to it. By passing a slice, you actually pass two pieces of information: how much you want to read (the length of the slice) and where to put the data that was read (the underlying array of the slice).

How to do it...

1. Create a byte slice large enough to hold the data you want to read:

   buffer := make([]byte,1024)

2. Read the data into the byte slice:

   nRead, err := reader.Read(buffer)

3. Check how much was read. The number of bytes actually read may be smaller than the buffer size:

   buffer = buffer[:nRead]

4. Check the error. If the error is io.EOF, then the...