[fix] Add ecdhCurve option (#1228)

Support ecdhCurve option as discussed in #1227.

lib/WebSocket.js

@@ -472,6 +472,7 @@ function initAsServerClient (socket, head, options) {
  * @param {Boolean} options.rejectUnauthorized Verify or not the server certificate
  * @param {String} options.passphrase The passphrase for the private key or pfx
  * @param {String} options.ciphers The ciphers to use or exclude
+ * @param {String} options.ecdhCurve The curves for ECDH key agreement to use or exclude
  * @param {(String|String[]|Buffer|Buffer[])} options.cert The certificate key
  * @param {(String|String[]|Buffer|Buffer[])} options.key The private key
  * @param {(String|Buffer)} options.pfx The private key, certificate, and CA certs
@@ -498,6 +499,7 @@ function initAsClient (address, protocols, options) {
     rejectUnauthorized: null,
     passphrase: null,
     ciphers: null,
+    ecdhCurve: null,
     cert: null,
     key: null,
     pfx: null,
@@ -598,13 +600,15 @@ function initAsClient (address, protocols, options) {
     options.checkServerIdentity ||
     options.passphrase ||
     options.ciphers ||
+    options.ecdhCurve ||
     options.cert ||
     options.key ||
     options.pfx ||
     options.ca
   ) {
     if (options.passphrase) requestOptions.passphrase = options.passphrase;
     if (options.ciphers) requestOptions.ciphers = options.ciphers;
+    if (options.ecdhCurve) requestOptions.ecdhCurve = options.ecdhCurve;
     if (options.cert) requestOptions.cert = options.cert;
     if (options.key) requestOptions.key = options.key;
     if (options.pfx) requestOptions.pfx = options.pfx;