api/server, dockerversion: modify context key

Signed-off-by: KimMachineGun <geon0250@gmail.com>

api/server/httputils/httputils.go

@@ -12,10 +12,8 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
-type contextKey string
-
 // APIVersionKey is the client's requested API version.
-const APIVersionKey contextKey = "api-version"
+type APIVersionKey struct{}
 
 // APIFunc is an adapter to allow the use of ordinary functions as Docker API endpoints.
 // Any function that has the appropriate signature can be registered as an API endpoint (e.g. getVersion).
@@ -83,7 +81,7 @@ func VersionFromContext(ctx context.Context) string {
 		return ""
 	}
 
-	if val := ctx.Value(APIVersionKey); val != nil {
+	if val := ctx.Value(APIVersionKey{}); val != nil {
 		return val.(string)
 	}
 

api/server/middleware/version.go

@@ -58,7 +58,7 @@ func (v VersionMiddleware) WrapHandler(handler func(ctx context.Context, w http.
 		if versions.GreaterThan(apiVersion, v.defaultVersion) {
 			return versionUnsupportedError{version: apiVersion, maxVersion: v.defaultVersion}
 		}
-		ctx = context.WithValue(ctx, httputils.APIVersionKey, apiVersion)
+		ctx = context.WithValue(ctx, httputils.APIVersionKey{}, apiVersion)
 		return handler(ctx, w, r, vars)
 	}
 

api/server/server.go

@@ -129,8 +129,7 @@ func (s *Server) makeHTTPHandler(handler httputils.APIFunc) http.HandlerFunc {
 
 		// use intermediate variable to prevent "should not use basic type
 		// string as key in context.WithValue" golint errors
-		var ki interface{} = dockerversion.UAStringKey
-		ctx := context.WithValue(context.Background(), ki, r.Header.Get("User-Agent"))
+		ctx := context.WithValue(context.Background(), dockerversion.UAStringKey{}, r.Header.Get("User-Agent"))
 		handlerFunc := s.handlerWithGlobalMiddlewares(handler)
 
 		vars := mux.Vars(r)

dockerversion/useragent.go

@@ -10,7 +10,7 @@ import (
 )
 
 // UAStringKey is used as key type for user-agent string in net/context struct
-const UAStringKey = "upstream-user-agent"
+type UAStringKey struct{}
 
 // DockerUserAgent is the User-Agent the Docker client uses to identify itself.
 // In accordance with RFC 7231 (5.5.3) is of the form:
@@ -39,9 +39,9 @@ func DockerUserAgent(ctx context.Context) string {
 func getUserAgentFromContext(ctx context.Context) string {
 	var upstreamUA string
 	if ctx != nil {
-		var ki interface{} = ctx.Value(UAStringKey)
+		var ki interface{} = ctx.Value(UAStringKey{})
 		if ki != nil {
-			upstreamUA = ctx.Value(UAStringKey).(string)
+			upstreamUA = ctx.Value(UAStringKey{}).(string)
 		}
 	}
 	return upstreamUA