v3 refactor (#1868)

* Move to v3

Co-authored-by: Ben Toogood <bentoogood@gmail.com>

runtime/runtime.go

@@ -7,11 +7,6 @@ import (
 )
 
 var (
-	// DefaultRuntime is default micro runtime
-	DefaultRuntime Runtime = NewRuntime()
-	// DefaultName is default runtime service name
-	DefaultName = "go.micro.runtime"
-
 	ErrAlreadyExists = errors.New("already exists")
 )