Yes you can do a global catch, but the error still happened, the functionality was faulty and you didn't handle it properly (you just showed the error, period).
I'm very very impressed by your code quality especially when this is just your first Go project. I'm an experienced Go developer btw. You're just so good.
The original output is very large but when gzipped it's surprisingly small. For example an app in my framework that gopherjs produces is like 1.2MB minified, but the gzipped one is just over 200kb, so no problem.
You could compare any language to machine language and you can say that language is less powerful. Go is not even close to the power of C and assembly. I'm not gonna even try to argue.
Your statement about Java or C# being "much nicer and faster" than Go is just plain wrong (Well if that's true then what's the reason to use Go?). In fact it falls in the same vein as Java or C# in performance, but it has the advantage of being native code. It isn't made to be a C contender. It's designed to be the simplest language to learn, the easiest to deploy, compile as fast as scripts, coding half as nice as Python and runs as fast as Java. Currently it excels at Cloud / server development.