Can't install Golang on Solaris via pkg - release/evaluation dependency

On a new installation of Solaris 11.3 on Sparc hardware, I'm trying to install Golang but am getting the following problem: # pkg install --accept developer/golang Creating Plan (Solver setup): | pkg install: No matching version of developer/golang can be installed: Reject: pkg://solaris/developer/golang@1.7-5.12.0.0.0.122.0 Reason: No version for 'require' dependency on release/evaluation can be found I'm new to Solaris but have installed a few other things via pkg and am also familiar with other packaging systems on Linux systems (rpm, apt, etc). What am I missing? The missing dependency on release/evaluation doesn't seem to be something I can install, and I've seen a post about 11.4 and FOSS software installs not having nasty "surprises" like 11.3 (which I think I've just found), but I can't see what those surprises are. NB: if it's relevant, I'm not currently using zones/etc, I'm just treating the system as one machine.