Go 1.13+ Unwrap Error stack to print type and contents to discover which error types are available for use with errors.As()

err_unwrap_stack.go

	if err != nil {
		for err != nil {
			fmt.Printf("%T: %#v\n", err, err)
			err = errors.Unwrap(err)
		}
	}
# Example Output
# *net.OpError: &net.OpError{Op:"read", Net:"tcp", Source:(*net.TCPAddr)(0xc00019df80), Addr:(*net.TCPAddr)(0xc00019dfb0), Err:(*os.SyscallError)(0xc000223b60)}
# *os.SyscallError: &os.SyscallError{Syscall:"read", Err:0x68}
# syscall.Errno: 0x68