ioEOF

io.EOF is a sentinel error value in the Go standard library that signals the end of input in I/O operations. Defined in the io package, it is used by many readers to indicate that no more data is available from the underlying source.

In Go's I/O model, the Read method of an io.Reader returns two values: the number of bytes read and an error. When the end of the input is reached, Read typically returns the number of bytes read (which may be zero) and the error io.EOF. Some implementations may return data and io.EOF together in the same call. Programs are expected to handle both the data and the end-of-file signal, continuing until an EOF is observed.

Common usage patterns involve looping over a stream and checking for io.EOF after each Read. With newer Go error inspection utilities, developers can also use errors.Is(err, io.EOF) to detect the end of input, which supports error wrapping and enhances compatibility.

io.EOF is not an indication of an exceptional failure; it is a normal condition that marks the natural end of a data stream. It can arise from various sources, such as files, network connections, or in-memory readers.

Related concepts include other errors in the io package (such as io.ErrShortBuffer and io.ErrUnexpectedEOF) and interfaces like io.Reader, io.Writer, and io.ReaderAt. Understanding io.EOF helps ensure correct and efficient handling of streaming data across different I/O sources.