go - "Merge" fields two structs of same type

Question

Looking at this struct:

type Config struct {
  path string
  id   string
  key  string
  addr string
  size uint64
}

Now I have a DefaultConfig intialized with some values and one loaded from a file, let's say FileConfig. I want both structs to me merged, so that I get a Config with the content of both structs. FileConfig should override anything set in DefaultConfig, while FileConfig may not have all fields set. (Why this? Because a potential user may not know the default value, so removing that entry would be equivalent to setting the default - I think)

I thought I'd need reflection for this:

 func merge(default *Config, file *Config) (*Config) {
  b := reflect.ValueOf(default).Elem()
  o := reflect.ValueOf(file).Elem()

  for i := 0; i < b.NumField(); i++ {
    defaultField := b.Field(i)
    fileField := o.Field(i)
    if defaultField.Interface() != reflect.Zero(fileField.Type()).Interface() {
     defaultField.Set(reflect.ValueOf(fileField.Interface()))
    }
  }

  return default
 }

Here I am not sure:

• If reflection is needed at all
• There may be easier ways to do this

Another issue I see here is that checking for zero values may be tricky: what if the overriding struct intends to override with a zero value? Luckily, I don't think it applies to my case - but this becomes a function, it may become a problem later

Answer 1

Waitting for answers