public AsyncRestBuilder withParam(String key, String value) {
        this.params.put(key, value);
        return this;
    }
public AsyncRestBuilder withParam ( String key , String value ) { this . params . put ( key , value ) ; return this ; }
Adds an URL query parameter to the request. Using a key twice will
result in the last call being taken into account.

@param key the parameter key.
@param value the parameter value.