code: func prf12(hashFunc func() hash.Hash) func(result, secret, label, seed []byte) {
  	return func(result, secret, label, seed []byte) {
  		labelAndSeed := make([]byte, len(label)+len(seed))
  		copy(labelAndSeed, label)
  		copy(labelAndSeed[len(label):], seed)
  
  		pHash(result, secret, labelAndSeed, hashFunc)
  	}
  }
docs: // prf12 implements the TLS 1.2 pseudo-random function, as defined in RFC 5246, section 5.