adding basic gocron-gorm-lock functionality. (#1)

Author: manuelarte

README.md

@@ -1,2 +1,68 @@
 # gocron-gorm-lock
 A gocron locker implementation using gorm
+
+## install
+
+```
+go get github.com/go-co-op/gocron-gorm-lock
+```
+
+## usage
+
+Here is an example usage that would be deployed in multiple instances
+
+```go
+package main
+
+import (
+	"fmt"
+
+	"github.com/go-co-op/gocron"
+	gormlock "github.com/go-co-op/gocron-gorm-lock"
+	"gorm.io/gorm"
+	"time"
+)
+
+func main() {
+	var db * gorm.DB // gorm db connection
+	var worker string // name of this instance to be used to know which instance run the job
+	db.AutoMigrate(&CronJobLock{}) // We need the table to store the job execution
+	locker, err := gormlock.NewGormLocker(db, worker)
+	if err != nil {
+		// handle the error
+	}
+
+	s := gocron.NewScheduler(time.UTC)
+	s.WithDistributedLocker(locker)
+
+	_, err = s.Every("1s").Name("unique_name").Do(func() {
+		// task to do
+		fmt.Println("call 1s")
+	})
+	if err != nil {
+		// handle the error
+	}
+
+	s.StartBlocking()
+}
+```
+
+## Prerequisites
+
+- The table cron_job_locks needs to exist in the database. This can be achieved, as an example, using gorm automigrate functionality `db.Automigrate(&CronJobLock{})`
+- In order to uniquely identify the job, the locker uses the unique combination of the job name + timestamp (by default with precision to seconds).
+
+## FAQ
+
+- Q: The locker uses the unique combination of the job name + timestamp with seconds precision, how can I change that?
+  - A: It's possible to set how to create the job identifier, here is an example to set an hour precision:
+    ```go
+	locker, err := gormlock.NewGormLocker(db, "local",
+		gormlock.WithJobIdentifier(
+			func(ctx context.Context, key string) string {
+				return time.Now().Truncate(60 * time.Minute).
+					Format("2006-01-02 15:04:05.000")
+			},
+		),
+	)
+    ```

go.mod

@@ -1,3 +1,59 @@
 module github.com/go-co-op/gocron-gorm-lock
 
 go 1.20
+
+require (
+	github.com/go-co-op/gocron v1.31.0
+	github.com/stretchr/testify v1.8.4
+	github.com/testcontainers/testcontainers-go v0.22.0
+	github.com/testcontainers/testcontainers-go/modules/postgres v0.22.0
+	gorm.io/driver/postgres v1.5.2
+	gorm.io/gorm v1.25.2
+)
+
+require (
+	dario.cat/mergo v1.0.0 // indirect
+	github.com/Azure/go-ansiterm v0.0.0-20210617225240-d185dfc1b5a1 // indirect
+	github.com/Microsoft/go-winio v0.6.1 // indirect
+	github.com/cenkalti/backoff/v4 v4.2.0 // indirect
+	github.com/containerd/containerd v1.7.3 // indirect
+	github.com/cpuguy83/dockercfg v0.3.1 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/docker/distribution v2.8.2+incompatible // indirect
+	github.com/docker/docker v24.0.5+incompatible // indirect
+	github.com/docker/go-connections v0.4.0 // indirect
+	github.com/docker/go-units v0.5.0 // indirect
+	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/golang/protobuf v1.5.3 // indirect
+	github.com/google/uuid v1.3.0 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a // indirect
+	github.com/jackc/pgx/v5 v5.3.1 // indirect
+	github.com/jinzhu/inflection v1.0.0 // indirect
+	github.com/jinzhu/now v1.1.5 // indirect
+	github.com/klauspost/compress v1.16.0 // indirect
+	github.com/magiconair/properties v1.8.7 // indirect
+	github.com/moby/patternmatcher v0.5.0 // indirect
+	github.com/moby/sys/sequential v0.5.0 // indirect
+	github.com/moby/term v0.5.0 // indirect
+	github.com/morikuni/aec v1.0.0 // indirect
+	github.com/opencontainers/go-digest v1.0.0 // indirect
+	github.com/opencontainers/image-spec v1.1.0-rc4 // indirect
+	github.com/opencontainers/runc v1.1.5 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/robfig/cron/v3 v3.0.1 // indirect
+	github.com/sirupsen/logrus v1.9.0 // indirect
+	go.uber.org/atomic v1.9.0 // indirect
+	golang.org/x/crypto v0.8.0 // indirect
+	golang.org/x/exp v0.0.0-20230510235704-dd950f8aeaea // indirect
+	golang.org/x/mod v0.9.0 // indirect
+	golang.org/x/net v0.9.0 // indirect
+	golang.org/x/sys v0.8.0 // indirect
+	golang.org/x/text v0.9.0 // indirect
+	golang.org/x/tools v0.7.0 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20230525234030-28d5490b6b19 // indirect
+	google.golang.org/grpc v1.57.0 // indirect
+	google.golang.org/protobuf v1.30.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)