code: public RestTemplateBuilder setConnectTimeout(Duration connectTimeout) {
  		return new RestTemplateBuilder(this.detectRequestFactory, this.rootUri,
  				this.messageConverters, this.requestFactorySupplier,
  				this.uriTemplateHandler, this.errorHandler, this.basicAuthentication,
  				this.restTemplateCustomizers,
  				this.requestFactoryCustomizer.connectTimeout(connectTimeout),
  				this.interceptors);
  	}
docs: Sets the connection timeout on the underlying {@link ClientHttpRequestFactory}.
  @param connectTimeout the connection timeout
  @return a new builder instance.
  @since 2.1.0