C code

# gcc -Wall -o c-client c-client.c arith_clnt.c arith_xdr.c arith.h
# gcc -Wall -o c-server c-server.c arith_svc.c arith_xdr.c arith.h

Go code

# go build go-server.go procedures.go
# go build go-client.go procedures.go

You should be able to use C client with Go server and also Go client with C server.