I've programmed in both and as far as I can tell here's the best use case for each:
Go - I want to program explicitly and don't mind a little extra code or syntax to do it. I want close to the best performance possible and a single distributable binary. I don't mind being encouraged to "roll my own" api / web app rather than using a framework.
Crystal - I want to feel like I'm writing in Ruby, but with type checking at compile time and much better performance. I don't mind being a little less performant than other compiled languages. I want access to Rails/Sinatra-like frameworks for web/API apps rather than having to "roll my own".
Basically, if you want something quick and fun that can run in production, I love Crystal. If you want something that needs to be custom and highly performant, I love Go.
Go - I want to program explicitly and don't mind a little extra code or syntax to do it. I want close to the best performance possible and a single distributable binary. I don't mind being encouraged to "roll my own" api / web app rather than using a framework.
Crystal - I want to feel like I'm writing in Ruby, but with type checking at compile time and much better performance. I don't mind being a little less performant than other compiled languages. I want access to Rails/Sinatra-like frameworks for web/API apps rather than having to "roll my own".
Basically, if you want something quick and fun that can run in production, I love Crystal. If you want something that needs to be custom and highly performant, I love Go.