A naive approach to using CloudSolrClient, such as on this page: http://joelsolr.blogspot.com/2015/04/the-streaming-api-solrjio-basics.html - will not work: opening the stream will throw an IOException with an embedded NullPointerException.
This took me a while to figure out, and I think it would be good to either update the documentation or "fix" the constructor to set the needed streamContext as appropriate.
I found this snippet of code in TuppleStream.java, that seems to "almost" work without a streamContext:
if streamContext is null in the last statement, a NullPointerException will be thrown and open'ening the stream will fail.
This took me way too long time to figure out.