Create a thread-safety analysis linter

[prateek]

Came across some thread-safety macros Clang provides for C++, and it really makes me want the equivalent for Go.

We should create a linter to do this, it'd catch a lot of issues - ensuring all code paths in a function release any locks which are held, ensuring we hold a lock while executing a function and/or reading/writing a specified variable.

Here's the paper about the work done for Clang/C++: https://research.google.com/pubs/archive/42958.pdf