package context import ( "golang.org/x/net/context" ) type key int const ( mdKey = key(0) ) type Metadata map[string]string func GetMetadata(ctx context.Context) (Metadata, bool) { md, ok := ctx.Value(mdKey).(Metadata) return md, ok } func WithMetadata(ctx context.Context, md Metadata) context.Context { return context.WithValue(ctx, mdKey, md) }