wip: migrate to mono-repo. SPN has already been moved to spn/

spn/terminal/upstream.go

@@ -0,0 +1,16 @@
+package terminal
+
+import "time"
+
+// Upstream defines the interface for upstream (parent) components.
+type Upstream interface {
+	Send(msg *Msg, timeout time.Duration) *Error
+}
+
+// UpstreamSendFunc is a helper to be able to satisfy the Upstream interface.
+type UpstreamSendFunc func(msg *Msg, timeout time.Duration) *Error
+
+// Send is used to send a message through this upstream.
+func (fn UpstreamSendFunc) Send(msg *Msg, timeout time.Duration) *Error {
+	return fn(msg, timeout)
+}