What is it

Package os provides a platform-independent interface to operating system functionality.

The design is Unix-like, although the error handling is Go-like; failing calls return values of type error rather than error numbers.

Read

// read file
file, err := os.Open("file.go")
if err != nil {
	log.Fatal(err)
}

// read file content
imageBytes, err := os.ReadFile(imagePath)
if err != nil {
	log.Fatal(err)
}

// read file byte count
data := make([]byte, 100)

count, err := file.Read(data)
if err != nil {
	log.Fatal(err)
}

fmt.Printf("read %d bytes: %q\n", count, data[:count])

Write

// write to byte array
byteArray := []byte("to be written to a file\n")

err := os.WriteFile("file.txt", byteArray, permissions)

if err != nil { ... }