pkg: add grpcutil package (#1032)

pkg/grpcutil/grpcutil.go

@@ -0,0 +1,31 @@
+// Package grpcutil contains functions for interacting with gRPC.
+package grpcutil
+
+import (
+	"context"
+
+	"google.golang.org/grpc/metadata"
+)
+
+// SessionIDMetadataKey is the key in the metadata.
+const SessionIDMetadataKey = "sessionid"
+
+// WithOutgoingSessionID appends a metadata header for the session ID to a context.
+func WithOutgoingSessionID(ctx context.Context, sessionID string) context.Context {
+	return metadata.AppendToOutgoingContext(ctx, SessionIDMetadataKey, sessionID)
+}
+
+// SessionIDFromGRPCRequest returns the session id from the gRPC request.
+func SessionIDFromGRPCRequest(ctx context.Context) (sessionID string, ok bool) {
+	md, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return "", false
+	}
+
+	sessionIDs := md.Get(SessionIDMetadataKey)
+	if len(sessionIDs) == 0 {
+		return "", false
+	}
+
+	return sessionIDs[0], true
+}