It is better to find a developer that has experience with the language features you use rather than one that is experienced in the exact language you use. For example, I work on distributed systems in Java/GoLang/Python. We want candidates that understand how to write concurrent logic and stay away from people who are just Java web developers.

The big issue is doing a coding interview with candidates. We have a standard straightforward problem that candidates need to solve by filling in a stubbed out method. We have it in Java and have ported it to GoLang. If we have to interview a candidate who does not know either of those languages, we would need to find a language that the candidate knows and we know well enough to port the problem to. We would also have some difficulty digging in to design specifics like choice of concurrency primitives.