Read a whole file with os.ReadFile

Most DevOps work touches files: config files, logs, certificates, templates. The simplest way to read one in Go is os.ReadFile, which slurps the whole file into memory in a single call.

It takes a path and returns two values: the file contents and an error.

data, err := os.ReadFile("/etc/app.conf")
if err != nil {
    fmt.Println("could not read file:", err)
    return
}

Reading a file can fail for many ordinary reasons: the path is wrong, the file was deleted, or the process lacks permission. The error is not optional noise, it is how you find out. Follow the same if err != nil rhythm you use everywhere else and handle the failure before you touch data.

The shape to memorise is one call followed by an error check:

data, err := os.ReadFile(path)
if err != nil {
    // handle it
}