What do you mean by "modules" here?

Go actually calls them packages.

I just prefer the term modules, as it was introduced by Mesa and CLU in the 70's.

Only languages based on C's primitive toolchain rely on basic separate compilation of translation units with textual includes for symbol definition.

Modular languages, that make use of better toolchains, couple the concept of separate compilation, with strong type checking across compilation boundaries and compiler managed metadata for the exported symbols.

Thanks for the explanation. Do you think the idea of implementation/interface separation, that C and Java allow easily, is also better in Go?

I didn't got your question.

Java packages are not that different from Go packages, in terms of CS concepts.

Except for the set of issues that are debated to death about Go, the language is quite modular in Mesa tradition.

Given Oberon's influence in Go's design[1], maybe you will find these books interesting,

From http://www.inf.ethz.ch/personal/wirth/ check "Algorithms and Data Structures", "Project Oberon", "Compiler Construction".

From http://ssw.jku.at/Research/Books/ check Object-Oriented Programming in Oberon-2.