Refactor Package structure

This commit cleans up the package structure, to make two new top-level
packages `internal` (for internal-use packages) and `pkg` (for general
shared utility code).

pkg/wait/wait.go

@@ -0,0 +1,31 @@
+package wait
+
+import (
+	"context"
+	"time"
+)
+
+// Wait repeatedly invokes f, until it returns true or the context is closed.
+// The invocation interval is determined by interval.
+func Wait(f func() bool, interval time.Duration, context context.Context) error {
+	// create a new timer
+	timer := time.NewTimer(interval)
+	if !timer.Stop() {
+		<-timer.C
+	}
+	defer timer.Stop()
+
+	for {
+		if f() {
+			return nil
+		}
+
+		// reset the timer, and wait for it again!
+		timer.Reset(interval)
+		select {
+		case <-timer.C:
+		case <-context.Done():
+			return context.Err()
+		}
+	}
+}