fix(coderd): fix memory leak in watchWorkspaceAgentMetadata (#10685)

Fixes #10550

testutil/go.go

@@ -0,0 +1,23 @@
+package testutil
+
+import (
+	"testing"
+)
+
+// Go runs fn in a goroutine and waits until fn has completed before
+// test completion. Done is returned for optionally waiting for fn to
+// exit.
+func Go(t *testing.T, fn func()) (done <-chan struct{}) {
+	t.Helper()
+
+	doneC := make(chan struct{})
+	t.Cleanup(func() {
+		<-doneC
+	})
+	go func() {
+		fn()
+		close(doneC)
+	}()
+
+	return doneC
+}