According to Wikipedia, Go's concurrency-model is not safe, and that's a huge problem in my opinion:

"There are no restrictions on how goroutines access shared data, making race conditions possible. Specifically, unless a program explicitly synchronizes via channels or mutexes, writes from one goroutine might be partly, entirely, or not at all visible to another, often with no guarantees about ordering of writes.[36] Furthermore, Go's internal data structures like interface values, slice headers, and string headers are not immune to race conditions, so type and memory safety can be violated in multithreaded programs that modify shared instances of those types without synchronization."