CustomRequestBody allows you the greatest amount of control over the request by directly supplying the body io.Reader, the length, and the content type header.

Client is a utility class representing a http client.

BeforeRetryCallback gets called with the response and error between a failure and a retry, but not before the first attempt.

CacheConditionCallback gets called to determine whether a given request should be looked up in the cache before making it for real.

CacheKeyFunction allows you to override the default key generator function, which is based only on method and url.

CacheResponseConditionCallback gets called after a successful request (no error) to determine whether the result should be cached.

MetricsCallbackFunction allows you to instrument the http client stack with callbacks in a variety of places.

RequestManipulatorCallback is an optional function you can provide that manipulates the http request before it is sent.

RetryConditionCallback is a function you need to provide that determines whether a retry should be attempted.