buildGoModule: supported structuredAttrs with subPackages

pkgs/build-support/go/module.nix

@@ -320,10 +320,15 @@ lib.extendMkDerivation {
               }
 
               getGoDirs() {
-                local type;
-                type="$1"
-                if [ -n "$subPackages" ]; then
-                  echo "$subPackages" | sed "s,\(^\| \),\1./,g"
+                local -r type="$1"
+
+                # Support strucuredAttrs, they are not space seperated
+                local -a subPackagesArray
+                concatTo subPackagesArray subPackages
+
+                # Outputs each element prefixed with './' if the array is not empty
+                if [[ ''${#subPackagesArray[@]} -gt 0 ]]; then
+                  echo "''${subPackagesArray[*]/#/./}"
                 else
                   find . -type f -name \*$type.go -exec dirname {} \; | grep -v "/vendor/" | sort --unique | grep -v "$exclude"
                 fi