Node.js v6 will go EOL at the end of April 2019, and already two of the production dependencies of the client have already dropped support for it, and soon others will do *(as well as development dependencies)*.
Furthermore, since Node.js will go in EOL it will never get security patches, plus, also OpenSSL-1.0.2 will go EOL [this year](https://github.com/nodejs/Release#release-schedule); to avoid risks for the client users it is better to drop support for Node.js v6 right away.
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