Comment by saclark11

You can do this in Go by making a type declaration defining a function and then adding a method with the same signature on that type, which calls the function. The Go standard library does exactly this with the `HandlerFunc` type [1].

  // The HandlerFunc type is an adapter to allow the use of
  // ordinary functions as HTTP handlers. If f is a function
  // with the appropriate signature, HandlerFunc(f) is a
  // [Handler] that calls f.
  type HandlerFunc func(ResponseWriter, *Request)
  
  // ServeHTTP calls f(w, r).
  func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {
      f(w, r)
  }

[1]: https://cs.opensource.google/go/go/+/refs/tags/go1.25.4:src/...