splitted go and expr function bindings in dedicated source files

bind-go-functions.go

@@ -0,0 +1,19 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// bind-go-function.go
+package expr
+
+// ---- Linking with Go functions
+type golangFunctor struct {
+	baseFunctor
+	f FuncTemplate
+}
+
+func NewGolangFunctor(f FuncTemplate) *golangFunctor {
+	return &golangFunctor{f: f}
+}
+
+func (functor *golangFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
+	return functor.f(ctx, name, args)
+}