There's a lot to like about Java and C#, but here are a few things that Go improved upon that spring to mind. Note that in some cases, Java and C# may have caught up in the interim. Note also that some things (e.g., low-latency GC) understandably weren't available from day 0 in Go, but followed quickly:

* Static binaries by default

* Single, straightforward build system (no DSLs)

* Single, ubiquitous code formatter

* Minimal learning curve

* Zero-work package publishing

* Zero-work documentation generation and publication

* Testing framework out of the box

* Production-grade HTTP server out of the box

* Low latency GC out of the box

More generally, C# and Java have always seemed to have a philosophy of "make everything as abstract and configurable as possible, and make the user understand every configuration option in order to do anything (overwhelm the user with configuration)". Granted, I haven't used C# or Java seriously since Go was open sourced, so it's possible that these are among the things that improved in C# and Java following Go's release.

> how did Go raise the bar compared to something like Java or C#, the actual “blue-collar” languages?

For me, Go being combination of being well-thought-out, opinionated and batteries included took away the futile fanboi flamewars/bike-shedding: JBoss or WebSphere? Tabs or spaces? Struts or Spring?

For these reasons and more, Go is offers a more pleasant experience when working in a team. When reading code other's wrote,I encounter fewer surprises in the logic and project structure. Go codebases are easier to grok, IMO.