Add api_key parameter to DoSearch method

[hscells]

Recently ncbi added an api_key that allows users to register their tools to issue more requests. This should be included in the parameters to DoSearch.

https://www.ncbi.nlm.nih.gov/books/NBK25499/#chapter4.api_key__enforced_in_May_2018

If you don't mind I might be able to do this myself, I'm still learning how to use the tool.

Thank you!

[kortschak]

You are welcome to send a PR. Note that the requirement doesn't actually hit us since it applies to "sites that post more than 3 requests per second" and there is an enforced limit of 3 requests per second, however it is a worthwhile addition.

BTW This is not limited to DoSearch.

[kortschak]

The easy fix is to add the following line to Parameters

APIKey string `param:"api_key"`

This will fix all functions that take *Parameters, but I imagine the limits apply to Info, Post, Global, Spell and CitMatch which don't accept that parameter.

[hscells]

I did not notice that this utility contained the limit, that is a very nice addition!

That sounds like a fairly simple fix 👍