I was getting this error building on Mac OS X 10.12:
$ pwd
<$GOPATH>/src/github.com/getlantern/systray/example
$ go run .
# github.com/getlantern/systray
systray_darwin.m:132:22: error: use of undeclared identifier 'NSControlStateValueOn'
systray_darwin.m:134:22: error: use of undeclared identifier 'NSControlStateValueOff'
The `NSControlStateValueOn` and `NSControlStateValueOff` were not
defined because Mac OS versions prior to 10.14 don't define
`__MAC_10_14`.
From `/usr/include/Availability.h`:
> It is also possible to use the *_VERSION_MIN_REQUIRED in source code to make one
> source base that can be compiled to target a range of OS versions. It is best
> to not use the _MAC_* and __IPHONE_* macros for comparisons, but rather their values.
> That is because you might get compiled on an old OS that does not define a later
> OS version macro, and in the C preprocessor undefined values evaluate to zero
> in expresssions, which could cause the #if expression to evaluate in an unexpected
> way.
>
> #ifdef __MAC_OS_X_VERSION_MIN_REQUIRED
> // code only compiled when targeting Mac OS X and not iPhone
> // note use of 1050 instead of __MAC_10_5
> #if __MAC_OS_X_VERSION_MIN_REQUIRED < 1050
> // code in here might run on pre-Leopard OS
> #else
> // code here can assume Leopard or later
> #endif
> #endif
See #75, #92.