metadata: split context to incoming and outgoing

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

metadata/metadata.go

@@ -2,7 +2,6 @@
 package metadata
 
 import (
-	"context"
 	"net/textproto"
 	"sort"
 )
@@ -12,16 +11,14 @@ var (
 	HeaderPrefix = "Micro-"
 )
 
-type metadataKey struct{}
-
 // Metadata is our way of representing request headers internally.
 // They're used at the RPC level and translate back and forth
 // from Transport headers.
 type Metadata map[string]string
 
 var (
-	// DefaultMetadataSize used when need to init new Metadata
-	DefaultMetadataSize = 6
+	// defaultMetadataSize used when need to init new Metadata
+	defaultMetadataSize = 2
 )
 
 type Iterator struct {
@@ -72,12 +69,9 @@ func (md Metadata) Set(key, val string) {
 // Del is used to remove value from metadata
 func (md Metadata) Del(key string) {
 	// fast path
-	if _, ok := md[key]; ok {
-		delete(md, key)
-	} else {
-		// slow path
-		delete(md, textproto.CanonicalMIMEHeaderKey(key))
-	}
+	delete(md, key)
+	// slow path
+	delete(md, textproto.CanonicalMIMEHeaderKey(key))
 }
 
 // Copy makes a copy of the metadata
@@ -89,39 +83,10 @@ func Copy(md Metadata) Metadata {
 	return nmd
 }
 
-// Del deletes key from metadata
-func Del(ctx context.Context, key string) context.Context {
-	md, ok := FromContext(ctx)
-	if !ok {
-		md = New(0)
-	}
-	md.Del(key)
-	return context.WithValue(ctx, metadataKey{}, md)
-}
-
-// Set add key with val to metadata
-func Set(ctx context.Context, key, val string) context.Context {
-	md, ok := FromContext(ctx)
-	if !ok {
-		md = New(0)
-	}
-	md.Set(key, val)
-	return context.WithValue(ctx, metadataKey{}, md)
-}
-
-// Get returns a single value from metadata in the context
-func Get(ctx context.Context, key string) (string, bool) {
-	md, ok := FromContext(ctx)
-	if !ok {
-		return "", ok
-	}
-	return md.Get(key)
-}
-
 // New return new sized metadata
 func New(size int) Metadata {
 	if size == 0 {
-		size = DefaultMetadataSize
+		size = defaultMetadataSize
 	}
 	return make(Metadata, size)
 }