rest-assured/src/main/java/io/restassured/internal/http/HTTPBuilder.java
public void setProxy(String host, int port, String scheme) {
        getClient().getParams().setParameter(
                ConnRoutePNames.DEFAULT_PROXY,
                new HttpHost(host, port, scheme));
    }
public void setProxy(String host, int port, String scheme) {
        getClient().getParams().setParameter(
                ConnRoutePNames.DEFAULT_PROXY,
                new HttpHost(host, port, scheme));
    }
Set the default HTTP proxy to be used for all requests.

@param host   host name or IP
@param port   port, or -1 for the default port
@param scheme usually "http" or "https," or <code>null</code> for the default
@see HttpHost#HttpHost(String, int, String)