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