Only copy Transport exported fields (#5844)

* Only copy Transport exported fields

* Do not skip the copylocks `go vet` check

* Re-separate grove and ATC library imports

.github/workflows/go.vet.yml

@@ -48,8 +48,4 @@ jobs:
     - name: Install modules
       run: go mod vendor -v
     - name: go vet
-      run: |
-        skip_analyzers=(
-          -copylocks=false
-        )
-        go vet "${skip_analyzers[@]}" ./...
+      run: go vet ./...

.golangci.yml

@@ -29,8 +29,3 @@ linters:
   disable-all: true
   enable:
     - govet
-
-linters-settings:
-  govet:
-    disable:
-      - copylocks

grove/remap/remap.go

@@ -497,7 +497,8 @@ func makeTo(tosJSON []RemapRuleToJSON, rule remapdata.RemapRule, baseTransport *
 				return nil, fmt.Errorf("error parsing to %v proxy_url: %v", to.URL, toJSON.ProxyURL)
 			}
 			to.ProxyURL = proxyURL
-			newTransport := *baseTransport
+			// See b7953cc239 for the reasoning behind copying the Transport.
+			newTransport := *baseTransport.Clone()
 			if proxyURL != nil && proxyURL.Host != "" {
 				newTransport.Proxy = http.ProxyURL(proxyURL)
 			}