Help with task: Update Avro's internal schema cache to use a thread-safe class

[张亚坤]

Hello,I’m a Programmer in China,I want to try some open source projects now and 
I want to begin from some easy tasks,I have seen this on the website,Could I 
make a try with this?
I would like to help out with the task listed at 
https://helpwanted.apache.org/task.html?7016995e