You can call Go from C, but it's extremely slow and requires special handling of GC'd references (among other things). It's not really a suitable replacement for C bindings in many circumstances.
True on all accounts but you forgot the "easily" part. Installing JVM and then writing JNI wrappers isn't really easy reuse.
You just don't see Java or Go code (let alone both) used in programs predominantly written in another language.
You can call Go from C, or even from Java on Android out-of-the-box (and Objective C on iOS), for example.