I solved this problem in a simple way: using symbolic links!
-common
-libfile
-service1
-file1
-file2
-libfile -> ../common/libfile
-service2
-file3
-file4
-libfile -> ../common/libfile
Then, i just import libfile as usual inside any of the native services’ file and it works! When serverless zips the services it follows the links and actually creates a normal file, it works great.