feature request: avoid use of `new Function`

[llimllib]

I'd like to run my fastify server with --disallow-code-generation-from-strings for additional safety, and this library is preventing me from doing so.

Is the usage of eval (via new Function) in this library absolutely necessary, or could it be avoided?

Would you be open to a PR that removed it, if it is possible to avoid?

[mcollina]

I think it might be possible to degrade gracefully if those are not available. They are essential to achieve a certain level of speed.