Add CGO environment variables for Go compilation

Author: 0xAnarz

source/ports/go_port/source/README.md

@@ -65,6 +65,13 @@ In case of using precompiled binaries (in Linux), when running any application u
 export LD_LIBRARY_PATH="/gnu/store/`ls /gnu/store/ | grep metacall | head -n 1`/lib"
 ```
 
+`go build` may require to set CGO environment variables pointing to MetaCall libraries in case of undefined C headers during compilation :
+
+```sh
+export CGO_CFLAGS=-I"/gnu/store/`ls /gnu/store/ | grep metacall | head -n 1`/include"
+export CGO_LDFLAGS=-L"/gnu/store/`ls /gnu/store/ | grep metacall | head -n 1`/lib"
+```
+
 ## Testing
 
 For running tests: