why xdp.c modified doesnt show error?

[kolinfluence]

i did "go build ." and there's no error message to errors i purposely made on xdp.c
how do i show compile error for xdp.c? or no matter what i do with xdp.c, it will not be reflected at the end of the "xdp" program output?
with ref to:
https://github.com/cilium/ebpf/tree/master/examples/xdp

[ti-mo]

Please see my reply at #876 (comment). go build does not equal go generate.