honor proxy settings in the environment (#45)

Resolves #44

The default go http library honors settings from the environment with the built in ProxyFromEnvironment function. This change configures samproxy to use the same thing.

Coming along for the ride is an update to the circle ci config to get the build to run.

.circleci/config.yml

@@ -1,7 +1,7 @@
 version: 2.1
 
 orbs:
-  buildevents: honeycombio/[email protected].2
+  buildevents: honeycombio/[email protected].3
 
 executors:
   linuxgo:
@@ -16,6 +16,12 @@ jobs:
     steps:
       - buildevents/start_trace
 
+  # finish_trace:
+  #   executor: linuxgo
+  #   steps:
+  #     - buildevents/finish_trace:
+  #         success: true
+
   test:
     executor: linuxgo
     steps:
@@ -79,31 +85,25 @@ jobs:
             ghr -t ${GITHUB_TOKEN} -u ${CIRCLE_PROJECT_USERNAME} -r ${CIRCLE_PROJECT_REPONAME} -c ${CIRCLE_SHA1} ${CIRCLE_TAG} ./artifacts/samproxy_${CIRCLE_TAG:1:20}_amd64.deb
             ghr -t ${GITHUB_TOKEN} -u ${CIRCLE_PROJECT_USERNAME} -r ${CIRCLE_PROJECT_REPONAME} -c ${CIRCLE_SHA1} ${CIRCLE_TAG} ./artifacts/samproxy-${CIRCLE_TAG:1:20}-1.x86_64.rpm
 
-  finish_trace:
-    executor: linuxgo
-    steps:
-      - buildevents/finish_trace:
-          result: success
-
 workflows:
   build:
     jobs:
       - setup:
           filters:
             tags:
               only: /.*/
+      # - finish_trace:
+      #     requires:
+      #       - setup
+      #     filters:
+      #       tags:
+      #         only: /.*/
       - test:
           requires:
             - setup
           filters:
             tags:
               only: /.*/
-      - finish_trace:
-          requires:
-            - test
-          filters:
-            tags:
-              only: /.*/
       - build:
           requires:
             - test

cmd/samproxy/main.go

@@ -95,6 +95,7 @@ func main() {
 
 	// upstreamTransport is the http transport used to send things on to Honeycomb
 	upstreamTransport := &http.Transport{
+		Proxy: http.ProxyFromEnvironment,
 		Dial: (&net.Dialer{
 			Timeout: 10 * time.Second,
 		}).Dial,
@@ -103,6 +104,7 @@ func main() {
 
 	// peerTransport is the http transport used to send things to a local peer
 	peerTransport := &http.Transport{
+		Proxy: http.ProxyFromEnvironment,
 		Dial: (&net.Dialer{
 			Timeout: 3 * time.Second,
 		}).Dial,