See Limbo, Alef, Newsqueak, and Squeak.
Occam was also derived from CSP, but I don't think it's accurate to call it a direct ancestor to Go.
https://en.wikipedia.org/wiki/Limbo_(programming_language)
Alef was Phil Winterbottom, yes.
The Squeak paper (http://ordiecole.com/squeak/cardelli_squeak1985.pdf) was 1985, so let's assume the work was likely some time in 1984. That would follow the Blit terminal work (paper in 1982), which seems reasonable. Newsqueak, Alef, and Limbo followed in that order.
occam 1 was 1983, so it seems reasonable that Cardelli & Pike were aware of it, although it's not cited in the paper, so perhaps they weren't.
The Newsqueak TR is from 1994, although it seems likely the work was done earlier. The TR doesn't contain any formal citations, but the text describes the language: "syntax and basic semantics come from C, while the message-passing primitives come from CSP". I think it's a little odd that it doesn't mention occam, as I think it was widely known by the mid-80s as a successful use of the CSP concepts, and Newsqueak must have been somewhere in the range 1985-1994.
Alef is described as being derived from Newsqueak, but was released with Plan9 1st edition in 1992. Alef has "alt" and "par" constructs, which strongly suggest an occam influence.
That said, this talk (http://go-lang.cat-v.org/talks/slides/emerging-languages-cam...) from Rob Pike identifies occam (and Erlang) as a distinct evolutionary branch from CSP.
I guess we'd need to ask to be sure. Party time in Putney?
https://stackoverflow.com/questions/32651557/golang-main-dif...
Then there was a generation-long pause. Then Go!