code: func masterFromPreMasterSecret(version uint16, suite *cipherSuite, preMasterSecret, clientRandom, serverRandom []byte) []byte {
  	seed := make([]byte, 0, len(clientRandom)+len(serverRandom))
  	seed = append(seed, clientRandom...)
  	seed = append(seed, serverRandom...)
  
  	masterSecret := make([]byte, masterSecretLength)
  	prfForVersion(version, suite)(masterSecret, preMasterSecret, masterSecretLabel, seed)
  	return masterSecret
  }
docs: // masterFromPreMasterSecret generates the master secret from the pre-master
  // secret. See http://tools.ietf.org/html/rfc5246#section-8.1