A constructor is just a function though... If I add a new field to a Java class and fail to add its initialization to the constructor, I have the exact same problem because Java initializes the field to its default value when the constructor is called.

You are correct that every situation where the struct in Go is initialized "bare" would need to be addressed if a field is added, but Go considers this a feature, not a bug (and, conversely, considers "bare initialization" of structs at dozens of places in your code to be bad practice if that struct could ever grow new fields). If you're bare-initializing structs, you're comfortable using them in a "loosey-goosey" context where zero-initialized fields are permitted (or, better, useful... https://www.youtube.com/watch?v=PAAkCSZUG1c&t=6m25s). In Go, the issue of required structure is addressed by wrapping the struct in an interface and then providing a function in the package that can create an instance of the interface. Used in that way, you get something very similar to a Java class (though Go doesn't force you into the "everything is a class" paradigm that Java demands).