code: func buildCipherSuites() []uint16 {
  	pref := preferredCipherSuite()
  	for _, suite := range gcmSuites {
  		if suite == pref {
  			// Go preferred an AES-GCM suite. Use those first.
  			return append(gcmSuites, append(chaChaSuites, otherSuites...)...)
  		}
  	}
  	// Use ChaCha20 at the top, then AES-GCM etc.
  	return append(chaChaSuites, append(gcmSuites, otherSuites...)...)
  }
docs: // buildCipherSuites returns a list of cipher suites with either AES-GCM or
  // ChaCha20 at the top. This takes advantage of the CPU detection that the
  // TLS package does to create an optimal cipher suite list for the current
  // hardware.