You could make a case that concurrency primitives weren't mainstream in programming languages at the time. But there's not a strong case for saying that Go introduced new concurrency primitives unless you just ignore the history of programming and programming languages. Nothing in Go's concurrency model was new. Not quite mainstream, sure. But not new. [EDIT: By primitives I take you to mean built-in to the language, not brought in via libraries like pthreads or something.]
I'd also question the statement that "native binaries" were not mainstream. That seems to ignore a lot of code out there, including the C++ code that Go was (in part) meant to replace at Google.
Defer as syntax is maybe new? But some form of finally construct was in a lot of languages used at the time Go was developed. Defer flattens the code by reducing indentation levels, but it introduced nothing new in terms of concepts that weren't already being used by programmers of mainstream languages.