chore: Add pubsub (#7)

* chore: Add pubsub

Exposes new in-memory and PostgreSQL pubsubs. This will be used for negotiating WebRTC connections.

* Don't run PostgreSQL tests on non-Linux

database/pubsub_test.go

@@ -0,0 +1,47 @@
+//go:build linux
+
+package database_test
+
+import (
+	"context"
+	"database/sql"
+	"testing"
+
+	"github.com/coder/coder/database"
+	"github.com/coder/coder/database/postgres"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPubsub(t *testing.T) {
+	t.Parallel()
+
+	t.Run("Postgres", func(t *testing.T) {
+		ctx, cancelFunc := context.WithCancel(context.Background())
+		defer cancelFunc()
+
+		connectionURL, close, err := postgres.Open()
+		require.NoError(t, err)
+		defer close()
+		db, err := sql.Open("postgres", connectionURL)
+		require.NoError(t, err)
+		defer db.Close()
+		pubsub, err := database.NewPubsub(ctx, db, connectionURL)
+		require.NoError(t, err)
+		defer pubsub.Close()
+		event := "test"
+		data := "testing"
+		ch := make(chan []byte)
+		cancelFunc, err = pubsub.Subscribe(event, func(ctx context.Context, message []byte) {
+			ch <- message
+		})
+		require.NoError(t, err)
+		defer cancelFunc()
+		go func() {
+			err = pubsub.Publish(event, []byte(data))
+			require.NoError(t, err)
+		}()
+		message := <-ch
+		assert.Equal(t, string(message), data)
+	})
+}