Reverted change to associate Transport to httpGetter.

This change caused a data race during async calls to groupcache.Get().
Also discovered `DefaultTransport` has per address connection pooling
only when the request was a success, which is sufficient for most use
cases.

CHANGELOG

@@ -4,19 +4,21 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [2.0.0-rc.3] - 2019-06-03
+## [2.0.0-rc.4] - 2019-06-04
 ### Changes
 * Now using golang standard `context.Context` instead of `groupcache.Context`.
 * HTTP requests made by `httpGetter` now respect `context.Context` done.
 * Moved `HTTPPool` config `Context` and `Transport` to `HTTPPoolOptions` for consist configuration.
-* Now Associating the transport with peer `httpGetter` so there is no need to
-  call `Transport` function for each request.
 * Now always populating the hotcache. A more complex algorithm is unnecessary
   when the LRU cache will ensure the most used values remain in the cache. The
   evict code ensures the hotcache does not overcrowd the maincache.
 * Changed import paths to /v2 in accordance with go modules rules
 * Fixed Issue where `DefaultTransport` was always used even if `Transport` was
   specified by the user.
+### Removed
+* Reverted change to associate `Transport` to `httpGetter`, Which caused a data
+  race. Also discovered `DefaultTransport` has per address connection pooling
+  only when the request was a success, which is sufficient for most use cases.
 
 ## [1.3.0] - 2019-05-23
 ### Added

http.go

@@ -222,7 +222,6 @@ func (p *HTTPPool) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 type httpGetter struct {
 	getTransport func(context.Context) http.RoundTripper
-	transport    http.RoundTripper
 	baseURL      string
 }
 
@@ -245,17 +244,12 @@ func (h *httpGetter) makeRequest(ctx context.Context, method string, in *pb.GetR
 	// Pass along the context to the RoundTripper
 	req = req.WithContext(ctx)
 
-	// Associate the transport with this peer so we don't need to
-	// call getTransport() every time a request is made.
-	if h.transport == nil {
-		if h.getTransport != nil {
-			h.transport = h.getTransport(ctx)
-		} else {
-			h.transport = http.DefaultTransport
-		}
+	tr := http.DefaultTransport
+	if h.getTransport != nil {
+		tr = h.getTransport(ctx)
 	}
 
-	res, err := h.transport.RoundTrip(req)
+	res, err := tr.RoundTrip(req)
 	if err != nil {
 		return err
 	}