You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: ulid.go
    path of file: ./repos/gotosocial/vendor/github.com/oklog/ulid
    
    the code of the file until where you have to start completion: // Copyright 2016 The Oklog Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a 
    
func (m *monotonic) random() (inc uint64, err error) {
	if m.inc <= 1 {
		return 1, nil
	}

	// Fast path for using a underlying rand.Rand directly.
	if m.rng != nil {
		// Range: [1, m.inc)
		return 1 + uint64(m.rng.Int63n(int64(m.inc))), nil
	}

	// bitLen is the maximum bit length needed to encode a value < m.inc.
	bitLen := bits.Len64(m.inc)

	// byteLen is the maximum byte length needed to encode a value < m.inc.
	byteLen := uint(bitLen+7) / 8

	// msbitLen is the number of bits in the most significant byte of m.inc-1.
	msbitLen := uint(bitLen % 8)
	if msbitLen == 0 {
		msbitLen = 8
	}

	for inc == 0 || inc >= m.inc {
		if _, err = io.ReadFull(m.Reader, m.rand[:byteLen]); err != nil {
			return 0, err
		}

		// Clear bits in the first byte to increase the probability
		// that the candidate is < m.inc.
		m.rand[0] &= uint8(int(1<<msbitLen) - 1)

		// Convert the read bytes into an uint64 with byteLen
		// Optimized unrolled loop.
		switch byteLen {
		case 1:
			inc = uint64(m.rand[0])
		case 2:
			inc = uint64(binary.LittleEndian.Uint16(m.rand[:2]))
		case 3, 4:
			inc = uint64(binary.LittleEndian.Uint32(m.rand[:4]))
		case 5, 6, 7, 8:
			inc = uint64(binary.LittleEndian.Uint64(m.rand[:8]))
		}
	}

	// Range: [1, m.inc)
	return 1 + inc, nil
}