Add support for password function to native

@@ -125,9 +125,25 @@ class ConnectionParameters {
 }
 
 getLibpqConnectionString(cb) {
-var params = []
-add(params, this, 'user')
-add(params, this, 'password')
+if (typeof this.password === 'function') {
+const pw = this.password();
+if (typeof pw === 'string') {
+return this._getLibpqConnectionString(cb, pw)
+}
+pw.then((pwString) => this._getLibpqConnectionString(cb, pwString)).catch((e) => cb(e))
+return
+}
+this._getLibpqConnectionString(cb);
+}
+
+_getLibpqConnectionString(cb, pw) {
+var params = [];
+add(params, this, 'user');
+if (pw != null) {
+params.push('password=' + quoteParamValue(pw))
+} else {
+add(params, this, 'password');
+}
 add(params, this, 'port')
 add(params, this, 'application_name')
 add(params, this, 'fallback_application_name')