Concurrency is a major stumbling block https://eng.uber.com/data-race-patterns-in-go/. Mutexs, conditional variable subtleties, wait groups, null pointer propagation, partial struct initialisations, channel lifetime coordination. tl;dr shared memory concurrency is hard.

The introduction of generics should make it easier to wrap these lower level concurrency primitives into higher level safe constructs without needing code generation or runtime type casting via interface{}.

Most devs also struggle to structure go programs in a way that makes them easily testable, but that’s true in a lot of languages.