If Google chose StandardML instead of Go, SML would win hands down in every way. Not many people or companies have tens to hundreds of millions sitting around to build a new language and ecosystem.
Dart is the language google is in a way selling, as the dev language for their new mobile platform flutter
Go, just happened, most available online material suggest that Go did really just happen
Rob pike have his taste, and build Go, in my opinion in the spirit of C, a pragmatic rather than theoretic effort
Go success, I think was not something that google really pushed for, it just happened because it seem many developer seem to prefer to use simpler languages, and deal with complexity "of using" a language, rather than learn a complex language and deal with the complexity "of learning" a language, developers are more engineers and craftsmen, rather than scientist
I'm not saying we should throw everything from Go away and all start programming in SML. I'm saying that people that worked on Go were too dogmatic to include pragmatic features that would have made it a better language. You can see this easily, from Rob Pike claiming that taxonomy is the least interesting kind of science or something like that, and thus a more useful type system is unnecessary. This is dogma.
Go didn't "just happen", Go had the support of Google to write a high quality and extensive standard library, and all the tooling around it. That takes a tremendous amount of time and money. SML or OCaml doesn't have that, so it's harder for them to compete. I assure you that if Go looked like a garbage collected Rust, while still having all the great tooling, the easy concurrency, the standard library and all that good stuff, its success would have been the same if not better.