Add a basic must package

We keep doing this all over the codebase. Let's just put it here once.

Author: nickstenning

must/must.go

@@ -0,0 +1,23 @@
+// Package must helps you do things that must not fail.
+//
+// Example:
+//
+//	var clusterURL = must.Get(url.Parse(...))
+//	var conn = must.Get(net.Dial("tcp", ...))
+//	must.Do(telemetry.Shutdown())
+package must
+
+// Do panics if err is non-nil.
+func Do(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+// Get returns v, and panics if err is non-nil.
+func Get[T any](v T, err error) T {
+	if err != nil {
+		panic(err)
+	}
+	return v
+}