I just downloaded a fresh copy of GoLand of the website. After browsing a project for a bit, I noticed that the "Find usages" only scopes to the current package.
I modified and tried several scopes, including "All Places" in the "Find Usage" settings : same result. Even though I'm not exactly sure what it does I tried "Invalidate caches / restart" and also "synchronize". None of them worked.
I'm not aware of anything else I can test.
It's a very recent version : GoLand 2018.1.1 - Build #GO-181.4445.70 (April 9, 2018).
JRE: 1.8.0_152-release-1136-b27 x86_64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o