public Builder setDefaultKeepAlive(final long defaultKeepAlive, final TimeUnit timeUnit) {
            this.connectionKeepAlive = TimeValue.of(defaultKeepAlive, timeUnit);
            return this;
        }
@return this instance.
@see #setConnectionKeepAlive(TimeValue)
httpclient5/src/main/java/org/apache/hc/client5/http/config/RequestConfig.java