Add PostgreSQL backend documentation

.gitignore

@@ -9,3 +9,6 @@ web/app/node_modules
 *.sqlite-wal
 
 custom-gcl
+
+# Docs build artifacts
+docs/build/

README.md

@@ -74,7 +74,7 @@ func runWorker(ctx context.Context, mb backend.Backend) {
 
 ### Backend
 
-The backend is responsible for persisting the workflow events. Currently there is an in-memory backend implementation for testing, one using [SQLite](http://sqlite.org), one using MySql, and one using Redis.
+The backend is responsible for persisting the workflow events. Currently there is an in-memory backend implementation for testing, one using [SQLite](http://sqlite.org), one using MySQL, one using PostgreSQL, and one using Redis.
 
 ```go
 b := sqlite.NewSqliteBackend("simple.sqlite")

backend/postgres/README.md

@@ -0,0 +1,8 @@
+# PostgreSQL backend
+
+## Adding a migration
+
+1. Install [golang-migrate/migrate](https://github.com/golang-migrate/migrate)
+1. ```bash
+   migrate create -ext sql -dir ./db/migrations -seq <name>
+   ```

docs/source/includes/_backends.md

@@ -1,6 +1,6 @@
 # Backends
 
-There are three backend implementations maintained in this repository. Some backend implementations have custom options and all of them accept:
+There are four backend implementations maintained in this repository. Some backend implementations have custom options and all of them accept:
 
 - `WithStickyTimeout(timeout time.Duration)` - Set the timeout for sticky tasks. Defaults to 30 seconds
 - `WithWorkflowLockTimeout(timeout time.Duration)` - Set the timeout for workflow task locks. Defaults to 1 minute
@@ -61,6 +61,31 @@ See `migrations/mysql` for the schema and migrations. Main tables:
 - `activities` - Queue of pending activities
 - `attributes` - Payloads of events
 
+## PostgreSQL
+
+```go
+func NewPostgresBackend(host string, port int, user, password, database string, opts ...option)
+```
+
+Create a new PostgreSQL backend instance with `NewPostgresBackend`.
+
+### Options
+
+- `WithPostgresOptions(f func(db *sql.DB))` - Apply custom options to the PostgreSQL database connection
+- `WithApplyMigrations(applyMigrations bool)` - Set whether migrations should be applied on startup. Defaults to `true`
+- `WithBackendOptions(opts ...backend.BackendOption)` - Apply generic backend options
+
+
+### Schema
+
+See `migrations/postgres` for the schema and migrations. Main tables:
+
+- `instances` - Tracks workflow instances. Functions as instance queue joined with `pending_events`
+- `pending_events` - Pending events for workflow instances
+- `history` - History for workflow instances
+- `activities` - Queue of pending activities
+- `attributes` - Payloads of events
+
 ## Redis
 
 ```go

docs/source/index.html.md

@@ -25,7 +25,7 @@ go-workflows is an embedded engine for orchestrating long running processes or "
 
 It borrows heavily from [Temporal](https://github.com/temporalio/temporal) (and since it's a fork also [Cadence](https://github.com/uber/cadence)) as well as Azure's [Durable Task Framework (DTFx)](https://github.com/Azure/durabletask). Workflows are written in plain Go.
 
-go-workflows support pluggable backends with official implementations for Sqlite, MySql, and Redis.
+go-workflows support pluggable backends with official implementations for Sqlite, MySQL, PostgreSQL, and Redis.
 
 See also the following blog posts: