1. It does have its own package manager but good luck actually finding packages. golang.org's list is out of date and so is every other resource.
This is a serious problem IMO.
2. The third party web libs are pretty poor. I'm a big fan of Express for Node and prefer just a little bit of goodies ontop of something minimal.
A lot of people like Sinatra/Flask so I'm not the only one who likes this. There's nothing like this in Go.
We have the bits and pieces to make it but no one has stepped up. Right now developing anything for the web with Go is just too annoying, you have to create so many things that literally every other language has had solved for years.
If both of these problems were solved I would insta switch to Go for everything and never look back. It's just so pleasant to program in for all the points you mentioned + more.