Expose http.Client

[enj]

I am trying to use this library with Google App Engine which does not allow one to use the standard library to make HTTP requests. I ran into a similar issue with a Twitter API, but was able to replace the http.Client since it was exposed in the API.

I believe a change like this could allow for a similar capability:

// This struct contains all the funcitonality
// of interacting with the Google Maps Geocoding Service
type GoogleGeocoder struct{
    HttpClient    *http.Client
}

...

// Issues a request to the google geocoding service and forwards the passed in params string
// as a URL-encoded entity.  Returns an array of byes as a result, or an error if one occurs during the process.
func (g *GoogleGeocoder) Request(params string) ([]byte, error) {
    if g.HttpClient == nil {
        g.HttpClient = &http.Client{}
    }
    client := g.HttpClient
    ...

Thoughts?

[kellydunn]

I think this could be a valuable addition, especially since you could swap out the http client to a mock client for testing purposes.

My only piece of feedback is to "constant-ize" the newly instantiated &http.Client{} as DefaultHTTPClient, like so:

var DefaultHTTPClient = &http.Client{}

//...

func (g *GoogleGeocoder) Request(params string) ([]byte, error) {
  if g.HttpClient == nil {
    g.HttpClient = DefaultHTTPClient
  }
  client := g.HttpClient
}

Fwiw, I have a list of features that I'd like to see in a 1.0.0 release of golang-geo, and this one could be on that list, as I see it being valuable for all geocoders to have this ability.

[kellydunn]

Great, It's on master now.

@enj , want to try it out and let me know if there's anything missing? If all is well, I'll close out this ticket 😄 🍻

[enj]

Works like a charm, feel free to close. Thanks for the help.